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1 This article was downloaded by:[columbia University] On: 17 September 2007 Access Details: [subscription number ] Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: Registered office: Mortimer House, Mortimer Street, London W1T 3JH, UK Historical Biology An International Journal of Paleobiology Publication details, including instructions for authors and subscription information: Osteology and phylogeny of a new species of Araripesuchus (Crocodyliformes: Mesoeucrocodylia) from the Late Cretaceous of Madagascar Alan H. Turner a a Department of Geoscience, University of Iowa, Iowa City, IA, USA Online Publication Date: 01 January 2006 To cite this Article: Turner, Alan H. (2006) 'Osteology and phylogeny of a new species of Araripesuchus (Crocodyliformes: Mesoeucrocodylia) from the Late Cretaceous of Madagascar', Historical Biology, 18:3, To link to this article: DOI: / URL: PLEASE SCROLL DOWN FOR ARTICLE Full terms and conditions of use: This article maybe used for research, teaching and private study purposes. Any substantial or systematic reproduction, re-distribution, re-selling, loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.

2 Historical Biology, 2006; 18(3): Osteology and phylogeny of a new species of Araripesuchus (Crocodyliformes: Mesoeucrocodylia) from the Late Cretaceous of Madagascar ALAN H. TURNER Department of Geoscience, University of Iowa, 121 Trowbridge Hall, Iowa City, IA 52242, USA Abstract A new species of Araripesuchus present in the Maevarano Formation of Madagascar is described. The taxon is known from at least five individuals, including a nearly complete animal, three partial skulls and associated post-cranial remains, as well as disarticulated post-cranial elements. This large sample, coupled with CT-scans, allows a detailed description of its morphology. The new form shares a number of derived characters with Araripesuchus gomesii and Araripesuchus patagonicus, but is distinguished from them by the presence of four autapomorphies. Additionally, the new form lacks a number of derived features present in A. gomesii and A. patagonicus. Phylogenetic relationships of Araripesuchus are evaluated using a parsimony analysis including 29 mesoeucrocodylian taxa. In all of the most parsimonious trees the new taxon is recovered as sister group to A. gomesii þ A. patagonicus. Araripesuchus is diagnosed by five unambiguous synapomorphies and forms a clade with the Malagasy crocodyliform Mahajangasuchus insignis and peirosaurids. This group is depicted as more closely related to neosuchians than to notosuchians. When Araripesuchus wegeneri is included in the analysis, it is recovered as a member of the Araripesuchus clade. Although, its position in the clade is unresolved and character support is weak, this finding supports A. wegeneri as a valid species of Araripesuchus. Keywords: Crocodyliformes, osteology, Araripesuchus, Late Cretaceous, Madagascar, Maevarano formation Institutional Abbreviations: AMNH, American Museum of Natural History, New York; FMNH, Field Museum of Natural History, Chicago; GDM-DNPM, Divisao de Mineralogia e Geologia do Departmento Nacional da Produçao Mineral, Rio de Janeiro, Brazil; GSP-UM, Geological Survey of Pakistan-University of Michigan collection, Quetta; IVPP, Institute of Vertebrate Paleontology and Paleoanthropology, Beijing, People s Republic of China; MACN RN, Museo Argentino de Ciencias Naturales, Buenos Aires, Argentina. Rio Negro Collection; MNN, Musée National de Niger, Niamey, Republic of Niger; MUC PV, Museo de Geología y Paleontología de la Universidad Nacional del Comahue, Neuquén, Argentina; TMM, Texas Memorial Museum, Austin; UA, University of Antananarivo, Madagascar Introduction Ongoing fieldwork in the Mahajanga Basin of northwestern Madagascar is expanding our knowledge of an unusual Late Cretaceous Gondwanan fauna. Part of this work has focused on the Campanian to Maastrichtian age Maevarano Formation, which preserves a terrestrial and freshwater assemblage including fish, amphibians, snakes, crocodyliforms, mammals, and dinosaurs (Krause and Grine 1996, Forster et al. 1996, Krause et al. 1997, Asher and Krause 1998, Gottfried et al. 1998, Sampson et al. 1998, Buckley and Brochu 1999, Buckley et al. 2000, 2003, Forster and O Connor 2000, Carrano et al. 2002, Whatley and Buckley 2004). To this point, the described dinosaurian component is entirely saurischian, including armored sauropods, abelisaurid theropods, and several birds (Forster et al. 1996, 1998, Sampson et al. 1998, 2001, Forster and O Connor 2000, Carrano et al. 2002, Curry-Rogers 2002, Curry- Rogers and Forster 2004). Correspondence: A. H. Turner, Division of Paleontology, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10024, USA. turner@amnh.org ISSN print/issn online q 2006 Taylor & Francis DOI: /

3 256 A. H. Turner Figure 1. DGM-DNPM 432-R, Araripesuchus gomesii. Line interpretation of cranial sutures. A, Dorsal view. B, Ventral view. The crocodyliform component is extremely diverse, including at least seven separate taxa (Buckley et al. 1997). These include large taxa, such as Trematochampsa (Buffetaut and Taquet 1979, Rasmusson 2002) and Mahajangasuchus insignis (Buckley and Brochu 1999, 2001), a long-snouted form (Buckley et al. 2003), as well as smaller forms such as Simosuchus clarki (Buckley et al. 2000). Also recovered from these beds are crocodyliform remains that show a suite of derived features present in the smallbodied taxon Araripesuchus. This material has been referenced by previous authors (Buckley et al. 1997, Buckley and Brochu 1999) and is described here as it represents a new species of Araripesuchus. This conclusion is based on a number of autapomorphic characteristics as well as the retention of some plesiomorphic traits not exhibited in the South American taxa, Araripesuchus gomesii, Araripesuchus patagonicus and Araripesuchus buitreraensis (Pol and Apesteguía 2005). Since the taxon was first described, Araripesuchus has been placed within, or sister to, a number of mesoeucrocodylian groups (Price 1959, Gasparini 1971, Gasparini et al. 1991, Clark 1994, Wu et al. 1997, Buckley and Brochu 1999, Pol 1999, 2003, Buckley et al. 2000, Ortega et al. 2000, Pol and Norell 2004). Although its membership in Mesoeucrocodylia is unquestioned, at present its taxonomic and phylogenetic status remains unclear. Inclusion of new information from the Malagasy taxon clarifies aspects of Araripesuchus morphology and phylogenetic analysis places it in a clade that is the sister group to Neosuchia. Additionally, a number of authors have raised doubts regarding the membership of Araripesuchus (Michard et al. 1990, Kellner 1994, Ortega et al. 2000, Prasad and Lapparent de Broin 2002). The contaxonomic status of Araripesuchus wegeneri, described by Buffetaut (1981), with the South American species of Araripesuchus has been questioned. These hypotheses, however, were not tested phylogenetically. This study will test this hypothesis by including A. wegeneri in the phylogenetic analysis with other Araripesuchus species and a broad sample of mesoeucrocodylian taxa. Araripesuchus systematics and review of membership This section is not intended to provide a thorough redescription of each of these taxa. Rather, it discusses and comments on the other species referred to Araripesuchus and reviews our understanding of these members of the taxon. Araripesuchus gomesii Price 1959 The holotype of A. gomesii (DGM-DNPM 432-R; Figure 1) from the Early Cretaceous (Albian) Santana Formation of Brazil was initially described by Price (1959). It consists of a nearly complete, but poorly preserved, skull lacking much of the skull table and occiput posterior to the left orbit and right supratemporal fenestra. A nearly complete mandible is preserved in near articulation, but displaced to the left lateral side. The palatal region is well preserved and most of the sutures on the snout and preserved skull table can be discerned. An almost complete skeleton of A. gomesii was later recovered from the same formation (AMNH 24450; Hecht 1991). The specimen is preserved on two slabs

4 New Araripesuchus from Madagascar 257 Figure 2. MUCPV 269, Araripesuchus patagonicus. Skull in dorsal view (A) and ventral view (B). Scale ¼ 1 cm. showing both dorsal and ventral aspects. AMNH has been acid prepared from both sides revealing extraordinary preservation and detail. The specimen has been photographed and a brief description was published by Hecht (1991), however, given the completeness of the specimen a detailed and thorough description and discussion of this specimen is warranted. Araripesuchus patagonicus Ortega et al This taxon is known from a single block containing at least four individual specimens from the Early Cretaceous (Albian) Rio Limay Formation of Neuquén Province, Argentina described by Ortega et al. (2000). The holotype (MUC PV 269; Figures 2, 3) consists of a nearly complete skull and the anterior half of the postcranium. The anterior-most end of the rostrum is missing in the type and the dorsal armor obscures details of the vertebral series. MUC PV 269 preserves articulated forearms and scapulae. The skull was removed from the block and the ventral surface prepared to expose the palate. The other referred specimens (MUC PV 267, 268, 268b, 270, 283) comprise an additional skull as well as hindlimb and other post-cranial elements. I had the opportunity to examine this material and disagree with the original interpretation of a few skull features present in the type specimen. Ortega et al. (2000: 61) described the prefrontal as a narrow, bony band that runs parallel to the frontal. The prefrontal does not expand laterally to any Figure 3. MUCPV 269, Araripesuchus patagonicus. Revised line interpretation of cranial sutures. A, Dorsal view. B, Ventral view.

5 258 A. H. Turner Figure 4. MUCPV 267, Araripesuchus patagonicus. Relationship between prefrontal, lacrimal, maxilla, and nasal bones. A, Skull in right lateral view. B, Same image with line interpretation superimposed upon it. significant degree at the level of the anterior border of the orbits. The line drawing of the skull (p. 63: fig. 5) illustrates the authors interpretation. The suture between the prefrontal and lacrimal, illustrated as lying dorsally, nearly inline with the medial border of the orbit, is interpreted here to be a narrow crack. A prominent linear feature (highlighted by slight sediment in-filling) corresponds more closely to the location of the prefrontal/lacrimal suture in other mesoeucrocodylians. The other skull (MUC PV 267) preserves the full extent of the prefrontal/lacrimal contact corroborating this conclusion. Given this new interpretation (Figure 4), the size of the dorsal surface of the lacrimal and prefrontal is similar. With only the anteromedial-most edge of the prefrontal contacting the nasal bone, the condition in A. patagonicus does not differ greatly from that in A. gomesii. The rod-like postorbital bar of A. patagonicus is shown as flush with the body of the jugal in Ortega et al. s (2000: fig. 5) drawing. The authors (p. 61) note that unlike the holotype of Araripesuchus gomesii and specimen AMNH 24450, the insertion of the postorbital bar in the main body of the jugal is dermal, at least on its anterior edge. I was unable to corroborate this observation. In both skulls, the postorbital bar appears inset from the lateral margin of the body of the jugal. In fact, in the holotype, a low, but distinct, ridge marks the anteroventral border of the postorbital bar. It is my interpretation that the postorbital bar is inset and subdermal as it is in other Araripesuchus taxa. Araripesuchus wegeneri Buffetaut 1981 This species of Araripesuchus is known from the Early Cretaceous Elrhaz Formation of Gadoufaoua, Niger. The holotype GDF 700 (a nearly complete rostrum preserving right jugal and much of the palate; Figures 5, 6) was given a brief description by Buffetaut (1981). Clark (1986) also noted that two weathered braincases exist for Araripesuchus wegeneri that have not yet been described and Buffetaut and Taquet (1979) mention isolated vertebrae, dermal scutes, and limb bones that may pertain to this taxon. A published detailed study of this taxon is lacking, but as an African mesoeucrocodylian, it is of biogeographic importance and should, therefore, benefit from a more thorough description. Michard et al. (1990), Kellner (1994) and Ortega et al. (2000) have argued that this taxon should not be considered a species of Araripesuchus, citing a number of features reputed to distinguish it from other Araripesuchus species. I disagree, however, with their interpretation on some of the features. Ortega et al. (2000: 69) characterizes the dentary of A. wegeneri as having a deep, vertical and flat posterior lamina. This description of the lateral surface of the dentary is not completely correct. The holotype (GDF 700) shows the same dorsoventral flattening of the anterior dentary, as well as verticalization and mediolateral flattening of the posterior dentary, in roughly the same position as the other Araripesuchus taxa around the fifth or sixth maxillary tooth. The difference between A. patagonicus and A. wegeneri is perhaps over pronounced due to the poor preservation of GDF 700 and the slight dorsoventral compaction of the Patagonian taxon. Ortega et al. (2000: 69) note that the splenial of A. wegeneri forms more than half of the width of the ventral surface of the mandible. The splenial of A. wegeneri, however, does not form any more than half of the ventral mandibular width (Figures 5B, 6B). The authors description appears to stem from a misinterpretation due to slight dorsoventral compression of the left mandibular ramus and poor preservation of the right ramus in GDF 700. Other species of Araripesuchus have anterolaterally facing external nares (Price 1959, Hecht 1991,

6 New Araripesuchus from Madagascar 259 Figure 5. GDF 700, Araripesuchus wegeneri. Skull in dorsal view (A) and ventral view (B). Scale ¼ 1 cm. (Photographs courtesy of C. Brochu.) Ortega et al. 2000). I was unable to confirm the presence of the frontally directed external nares in A. wegeneri the anterior tip of the rostrum is eroded on GDF 700. The other features said to distinguish A. wegeneri from other Araripesuchus species was presence of five premaxillary teeth in A. wegeneri and the presence of denticles on the posterior maxillary teeth. Five premaxillary teeth are common among crocodylomorphs and five premaxillary teeth are present in the Malagasy Araripesuchus described in this study as well as the newly described Araripesuchus buitreraensis (Pol and Apesteguía 2005). This leaves denticulated posterior maxillary teeth as the only unambiguously unique feature distinguishing A. wegeneri from other Araripesuchus species (Figure 7). Based on this feature, isolated teeth from Cameroon were referred to aff. Araripesuchus (Brunet et al. 1990). Prasad and Lapparent de Broin Figure 6. GDF 700, Araripesuchus wegeneri. Line interpretation of cranial sutures. A, Dorsal view. B, Ventral view.

7 260 A. H. Turner Figure 7. GDF 700, Araripesuchus wegeneri. Close-up of maxillary teeth showing denticles on tooth margin. (Image from the photograph Serrette courtesy of F. de Lapparent de Broin.) (2002) noted the similarity between the teeth of A. wegeneri and aff. Araripesuchus and, based on this similarity, provisionally renamed A. wegeneri as aff. Hamadasuchus wegeneri. I find this conclusion suspect. Hamadasuchus rebouli is currently known from a fragmentary left dentary (Buffetaut 1994, though see Sues and Larsson 2002). Furthermore, ziphodont tooth morphology (laterally compressed with serrations) has proven to be of limited phylogenetic value (Langston 1956, Berg 1966, Hecht and Archer 1977, Turner and Calvo 2005) and is found in numerous crocodyliform taxa that do not show close phylogenetic affinities with one another, e.g. pristichampsines (Langston 1956), mekosuckines (Hecht and Archer 1977), Platyognathus (Wu and Sues 1996a), Sebecus (Colbert 1946), Eremosuchus (Buffetaut 1989), Mahajangasuchus (Buckley and Brochu 1999), Itasuchus (Price 1955), Iberosuchus (Antunes 1975). It is my view that the presence of ziphodont dentition in A. wegeneri is simply an autapomorphy of the species, with respect to other Araripesuchus species, and as such is not sufficient grounds for renaming the taxon. Although, it is a distinct and different tooth morphology, I do not see any compelling reason that such a character should be considered more phylogenetically significant than any other autapomorphic character. Relationships of Araripesuchus to other mesoeucrocodylians Since its initial description, Araripesuchus has proven difficult to place phylogenetically given that it preserves a combination of apparently primitive and derived characteristics (Hecht 1991). When Price (1959) first described Araripesuchus gomesii, he included it in Notosuchidae, noting its similarities with Notosuchus terrestris. This noted similarity included 18 characteristics (small to medium size, skull rather high with a short snout, orbits that are large and in a vertical position, a slightly inclined quadrate, postorbital bar slightly subdermal, external nares single or divided, internal nares formed by pterygoid and palatine, presence of an antorbital fenestra, a supratemporal fenestra smaller than the orbits, frontal may or may not participate in supratemporal fenestra, supraoccipital participates in cranial roof, a large external mandibular fenestra, splenials participate in the symphysis, dentition reduced in number and specialized, sculpture of cranial bones tend to irregular wrinkles, amphicoelous vertebrae, and dermal armor). Of course, it is now understood that almost all of these characters are widespread among crocodyliforms and plesiomorphic for Araripesuchus and Notosuchus (Clark 1986). Following this, Gasparini (1971) erected the suborder Notosuchia to include Notosuchus, Uruguaysuchus, Sphagesaurus and Araripesuchus. In addition, Gasparini (1971) noted similarities between Araripesuchus and Uruguaysuchus including them together in the Uruguaysuchidae. Characters given for this grouping were: an external nares terminating dorsally, the lack of a maxillo-palatal fenestra (this, it seems, was noting a distinction from Notosuchus, which possesses a maxillo-palatal fenestra), having a notch between the premaxilla and maxilla, larger number of teeth in the maxilla, and hypertrophied maxillary teeth (Gasparini 1971). None of these early suggestions were based on cladistic analyses. Early cladistic analyses (Clark 1986, 1994, Benton and Clark 1988) placed Araripesuchus as more closely related to neosuchians than Notosuchus (making Notosuchia, in the traditional sense, paraphyletic). This relationship is corroborated by a number of unambiguous apomorphies. These derived characters include: a premaxilla that forms little, if any, of the internarial bar; external nares dorsolaterally or dorsally oriented; a quadrate with a single fenestra; teeth enlarged in the middle of tooth row, with edge of maxilla extending outward at these points; and the dentary teeth posterior to tooth opposite premaxilla maxilla contact enlarged opposite smaller teeth in maxillary tooth row. Other synapomorphies supporting this relationship are a rostrum constricted at the contact of the premaxilla with maxilla forming a narrow slit, a moderate sized internal choana, and an antorbital fenestra smaller than the orbit.

8 New Araripesuchus from Madagascar 261 In subsequent work, phylogenetic analyses have placed Araripesuchus as the sister taxon of Sebecosuchia þ Trematochampsa þ Caririsuchus (Gasparini et al. 1991), as the sister to Neosuchia (Clark 1994, Ortega et al. 2000), as the sister to Libycosuchus þ Notosuchus (Wu et al. 1997), as the sister taxon of the clade Peirosauridae þ Mahajangasuchus þ Trematochampsa (Buckley and Brochu 1999, Buckley et al. 2000, Turner 2004, Turner and Calvo 2005), in an unresolved polytomy with Neosuchia and other basal mesoeucrocodylians (Larsson and Gado 2000), in an unresolved polytomy with Notosuchus and other notosuchians (Sereno et al. 2001), in an unresolved polytomy with a notosuchian clade and Neosuchia (Pol 2003), or as the sister taxon to a notosuchian clade (Pol and Norell 2003, Pol and Apesteguía 2005). Differences between these analyses are likely due to the sometimes large differences in dataset size and taxon sampling. Basically, two positions within basal mesoeucrocodylians have been proposed for Araripesuchus based on phylogenetic analysis. Some analyses depict Araripesuchus closer to notosuchians than neosuchians (Wu et al. 1997, Pol and Norell 2003, Pol and Apesteguía 2005) or closer to neosuchians than notosuchians (Clark 1994, Ortega et al. 2000, Buckley et al. 2000, Turner and Calvo 2005). Is Araripesuchus monophyletic? There has been no doubt about the sister relationship between A. gomesii and A. patagonicus (Ortega et al. 2000, Pol 2003, Pol and Norell 2003, Turner 2004). Therefore, this question of monophyly should perhaps be rephrased to ask, Is A. wegeneri properly considered a species of Araripesuchus? Efforts to remove the African taxon from Araripesuchus have been phenetic (Ortega et al. 2000) or based on dental morphology alone (Prasad and Lapparent de Broin 2002). Although, a distinct dental morphology, ziphodonty is no more or less indicative of higher level relationships than the shape of the prefrontal/ nasal contact and cannot be used to exclude a species from a taxon, even more so while other aspects of morphology are ignored. Is Araripesuchus a notosuchian? Answering this question proves difficult given a lack of consensus among phylogenetic analyses. In the most recent analyses, Araripesuchus has bounced among basal mesoeucrocodylians. In analyses that have a resolved position for Araripesuchus, two locations are consistently found and correspond to the historical perceptions of its systematic placement i.e. sister to Neosuchia (Benton and Clark 1988, Buckley and Brochu 1999, Buckley et al. 2000, Ortega et al. 2000, Brochu et al. 2002, Turner 2004, Turner and Calvo 2005) or sister to notosuchians (Wu et al. 1997, Pol and Norell 2003, Pol and Apesteguía 2005). Further taxon sampling among notosuchians and other nonneosuchians may be necessary to resolve these issues. Whether Araripesuchus is closely allied with notosuchians remains equivocal, but a number of characters support this grouping. A. gomesii, A. patagonicus, Notosuchus and Malawisuchus have lacrimals that contact the nasals along the medial and anterior border (character 12-1 in Clark 1994, Buckley and Brochu 1999, Buckley et al. 2000). This character, however, is also present in Theriosuchus (Owen 1879, Clark 1986). The frontal extends only slightly or not at all into the supratemporal fenestrae in Araripesuchus, Malawisuchus and Comahuesuchus (character 23-1 in Clark 1994, Buckley and Brochu 1999, Buckley et al. 2000). This feature is present in other crocodylomorphs (e.g. Protosuchus, Hesperosuchus). In Araripesuchus, Simosuchus, Uruguaysuchus and Malawisuchus the cheek teeth are constricted at the base of the crown (character in Buckley et al. 2000). In addition, A. gomesii, A. patagonicus, Anatosuchus, Comahuesuchus and Uruguaysuchus share the feature that the bar between the orbit and supratemporal fossa is narrow, with sculpturing on the anterior part only. Clark (1986) also noted that Baurusuchus, Sebecus, Libycosuchus, Notosuchus and Araripesuchus share a peculiar anterolaterally facing edge on the postorbital. On the post-cranium, Araripesuchus, Notosuchus, and Uruguaysuchus all have a flange on the anterolateral edge of the femur (Rusconi 1933, Pol 2005). Araripesuchus, however, also shares this feature with Mahajangasuchus and Trematochampsa (Buckley and Brochu 1999, Buckley et al. 2000). Biogeographic history Buffetaut and Taquet (1979) first noted the biogeographic importance of Araripesuchus. Like Sarcosuchus, Araripesuchus is one of few taxa with species present in both Africa and South America, and has been used as evidence for a close faunal link between these two landmasses during the Early Cretaceous (Buffetaut 1981, 1982, Buffetaut and Rage 1993, Gasparini 1996). With the discovery of the Malagasy Araripesuchus examined in this study, Araripesuchus is now found in three Gondwanan landmasses. That Araripesuchus is shared with Africa, South America and Madagascar makes it central to these questions of Late Cretaceous Gondwanan paleobiogeography as it provides a valuable test of the different biogeographic scenarios (Turner 2004). Methods Computed tomographic analysis To access the internal cranial morphology of the Malagasy Araripesuchus, the skulls of the UA 8720

9 262 A. H. Turner (holotype) and FMNH PR 2297 were scanned in June of 2002 at the high resolution X-ray computed tomography (CT) facility at the University of Texas at Austin. The ultra-high resolution subsystem CCD camera was employed with X-ray energies set to 120 kv and ma and left unfiltered. Fifteen slices were acquired per rotation using 1000 views (angular orientation) and two samples per view. The samples were scanned on an empty mount wedge, with no offset, a slice thickness of mm, and inter-slice spacing of mm. The field of reconstruction was 40 mm (maximum field of view mm), the reconstruction offset 5000, and the reconstruction scale 600. The coronal slice data was resliced in the sagittal and horizontal planes at an interslice spacing of mm. The interslice thickness for cutaway images was also mm. Images were archived as individual slices in 16-bit TIFF format data files. Data were processed by the author and Jessica Maisano using the original images reduced to an 8-bit file format. QuickTime slice-byslice animations were generated along the three orthogonal axes. All are unreduced from their original image size and are compressed using QuickTime s photo-jpg compression (quality: medium). Grayscale values for the images were leveled in Adobe Photoshop (15, 1, 210). The coronal movie (CorFlipHeadMatrix.mov) begins at the tip of the rostrum, proceeding posteriorly with each slice in anterior view. The horizontal movie (HorFlipHead- Matrix.mov) starts on the dorsal surface and passes ventrally with each slice in dorsal view. The sagittal movie (SagFlipHeadMatrix.mov) proceeds from left to right through the specimens which are in left lateral view. The coronal slices were also manipulated in Voxblast (VayTek, Inc., Fairfield, IA) to make three-dimensional models that rotate the specimen around the three orthogonal axes. Most of the matrix surrounding the specimens is fine-grained sandstone, the density of which does not vary much within each sample. The contrast between bone density and matrix density was high. This allowed for digital removal of the matrix for each of the CT images. A set of models were generated with the matrix present in the images (RollSpinHeadMatrix.mov, PitchSpinHeadMatrix.mov, YawSpinHeadMatrix. mov), with the matrix digitally removed (Roll- SpinHeadNomatrix.mov, PitchSpinHeadNomatrix. mov, YawSpinHeadNomatrix.mov), and with matrix gradually made transparent during the movement of the renderings (RollSpinHeadVoila.mov, PitchSpin- HeadVoila.mov, YawSpinHeadVoila.mov). All data files are unreduced from their original image size with levels adjusted in Adobe Photoshop (0, 1, 198) and compressed using QuickTime s photo-jpg compression (quality: medium). Lastly, a three dimensional cutaway movie along the coronal axis was also created. Examples of the images generated by the CT analysis can be found throughout this work. CT movies can be viewed at amnh.org/users/turner. Phylogenetic analysis Parsimony analysis consisted of equally weighted heuristic searches with 1000 random addition (RA) replicates and tree bisection and reconnection (TBR) branch-swapping run using PAUP* v4.0b10 (Swofford 2002). The ingroup consisted of 29 mesoeucrocodyliform taxa and the outgroup of three protosuchian taxa Protosuchus, Hemiprotosuchus and Orthosuchus. The dataset analyzed comprises 129 morphological characters that were equally weighted, with all multistate characters treated as unordered. Characters 1, 9, 15, 37, 45, 49, 67, 77, 79 and 111 represent potentially nested sets of character states or include presence/absence states. Ordering of these characters affects the tree length but not the number nor topology of the most parsimonious trees. Nodal support was examined using nonparametric bootstrapping, with 1000 bootstrap replicates, TBR branch-swapping, and 10 RA sequences. Decay indices were also calculated using TreeRot v2c (Sorenson 1999). Sensitivity analysis was conducted regarding the phylogenetic position of Araripesuchus with respect to Notosuchus and Notosuchia. Trees constraining the placement of Araripesuchus within Notosuchia, or as the sister group of Notosuchia were generated in MacClade v4.06 (Maddison and Maddison 2003). Additional heuristic searches were conducted in PAUP* using the enforce topological constraints option, keeping only those trees that were compatible with the constraint tree. The lengths of these trees were then compared to the length of the MPTs to determine how suboptimal these alternate topologies are. Systematic paleontology CROCODYLOMORPHA (Walker 1970) CROCODYLIFORMES (Hay 1930) MESOEUCROCODYLIA (Whetstone and Whybrow 1983) ARARIPESUCHUS TSANGATSANGANA, nov. sp. Etymology Tsangatsangana, Malagasy expression meaning just out for a walk, also used ironically for a long voyage. Usage here refers to this taxon s distant geographic location relative to other known Araripesuchus species.

10 New Araripesuchus from Madagascar 263 Holotype UA 8720, nearly complete skull lacking posterior portion beyond the supratemporal fenestrae. Paratypes A large nearly complete skull, including left and right hyoid, the first twelve presacral vertebrae with ribs, partial left and right scapulae, proximal end of right humerus, left ilium and proximal head of left femur, right femur lacking head, partial pubis and three damaged dorsal ribs, three damaged dorsal ribs, right coracoid, portion of the shaft of the right humerus, left calcaneum and astragalus (FMNH PR 2297); Partial skull, damaged right mandible, right jugal, left radius and ulna, partial obscured right radius, nearly complete vertebral column, sacrum, portions of left and right hindlimbs (FMNH PR 2298); Partial skull, left palpebral, left surangular and angular, right ilium, right dentary, right splenial, right angular, partial maxilla, dorsal and caudal vertebrae, dorsal ribs (FMNH PR 2299); dentaries (UA 8750, UA 8751, UA 8763, FMNH PR 2318); splenial (FMNH PR 2316); angular (UA 8754); premaxillae (FMNH PR 2334); maxillae (UA 8756, UA 8760, UA 8761, UA 8762, FMNH PR 2321); jugals (UA 8752, FMNH PR 2317, FMNH PR 2332); nasals (UA 8764); frontals (UA 8765, FMNH PR 2322); postorbital (FMNH PR 2315); palpebrals (UA 8757, FMNH PR 2336); cervicals (UA 8728, UA 8739, FMNH PR 2307, FMNH PR 2323); dorsals (UA 8722, UA , UA 8742, UA , UA 8774, FMNH PR ); sacrals (UA 8767, FMNH PR 2301, FMNH PR 2330); caudals (UA , UA 8735, FMNH PR 2308, FMNH PR 2309, FMNH PR 2330); dorsal ribs (UA 8732, UA 8733, UA 8755, FMNH PR 2334); chevrons (UA 8755); osteoderms (FMNH PR 2333); scapulae (UA 8779, FMNH PR 2313, FMNH PR 2334); coracoids (UA 8740, UA 8741, FMNH PR 2313); humeri (UA 8721, FMNH PR 2302, FMNH PR , FMNH PR 2340); radii (FMNH PR 2324, FMNH PR 2321, FMNH PR 2327, FMNH PR 2329, FMNH PR 2339); ulnae (UA 8758, FMNH PR 2324, FMNH PR 2326, FMNH PR 2327, FMNH PR 2339); pisiform (FMNH PR 2324); radialia (UA 8736, UA 8737, FMNH PR 2310, FMNH PR 2324, FMNH PR 2339); ulnaria (UA 8736, UA 8759, FMNH PR 2324, FMNH PR 2339); metacarpals (FMNH PR 2312, FMNH PR 2328); manual phalanges (FMNH PR 2312, FMNH PR 2328); manual unguals (FMNH PR 2328); ilia (FMNH PR 2301, FMNH PR 2303, UA 8768, FMNH PR 2330); ischium (FMNH PR 2330); pubes (UA 8776, UA 8777, UA 8778, FMNH PR 2330, FMNH PR 2331); femora (UA 8734, FMNH PR 2300, FMNH PR 2330, FMNH PR 2337); tibiae (FMNH PR 2300, FMNH PR 2330, FMNH PR 2335, FMNH PR 2337); fibulae (UA 8781, FMNH PR 2300, FMNH PR 2330, FMNH PR 2335); astragalus (FMNH PR 2330); metatarsals (UA 8736, UA 8780, FMNH PR 2319, FMNH PR 2330, FMNH PR 2337, FMNH PR 2338); pedal phalanges (UA 8743, UA 8744 UA 8746, FMNH PR 2311, FMNH PR 2319, FMNH PR 2330, FMNH PR 2337); pedal unguals: (UA 8736, FMNH PR 2330); unidentified phalanges (UA 8747 UA 8749, FMNH PR 2314); unidentified unguals (UA 8747 UA 8749, FMNH PR 2314). Horizon and locality The holotype and all referred material was discovered by a University of Antananarivo graduate student, Joseph Augustin Rabarison, on August 15, 1993 from a single locality, MAD This locality occurs within the Anembalemba Member of the Maevarano Formation (Campanian? Maastrichtian, Late Cretaceous), Mahajanga Basin, near the village of Berivotra in northwestern Madagascar (Krause et al. 1998, Rogers and Hartman 1998, Rogers et al. 2000; Figure 8). Diagnosis Differs from all other Araripesuchus species by possessing a hypertrophied 10th dentary tooth, nasals that do not contact the lacrimal, a premaxilla that forms little of the internarial bar, and a retroarticular process projecting from the dorsal part of the mandible and attenuating. Figure 8. Geographic location. A, Map of Mahajanga Basin showing exposures of Maevarano Formation (grayed area). Box near center of map indicates the study area. B, Map of Madagascar, showing location of Mahajanga Basin.

11 264 A. H. Turner Description: Skull and mandible General form and preservation Material for A. tsangatsangana is recovered in three associated blocks as well as a number of isolated remains. The holotype (UA 8720; Figures 9 13) is very well preserved and details much of the bone texture and cranial suture pattern. One other nearly complete skull (FMNH PR 2297; Figures 14 17), and four partial skulls (UA 8766, UA 8775, FMNH PR 2298, FMNH PR 2299; Figures 18, 28), are preserved in good condition. The holotype is isolated from the remainder of the material. The posteriormost portion of the skull is not preserved and the lower jaw is missing, except for a very small portion of the left surangular displaced adjacent to the left jugal. It is the smallest of the preserved skulls. FMNH PR 2297 is the largest of the five and is more complete but less well preserved than the holotype. FMNH PR 2297 preserves a fragmentary entire skull and lower jaw. The overall condition of this skull is poorer though, because moderate compaction during preservation rendered portions of the bone damaged and some sutures ambiguous. CT data were obtained for UA 8720 and FMNH PR These data provide detailed images and information on the internal cranial morphology of Araripesuchus. The partial skulls (UA 8766, UA 8775, FMNH PR 2298, FMNH PR 2299) provide a secondary source of information on internal cranial structures as well as aspects of the dorsal palate and external braincase. FMNH PR 2298 is a nearly complete individual. The skull consists of the posterior half. On both sides, it lacks much of the lateral dermal bones thereby providing access to portions of the chondrocranium and palatal dermatocranium. The frontal is present but no bone is anterior to this. The anterior portion of the right mandibular ramus is preserved, but compacted to the ventral surface of the skull. FMNH PR 2299 also is a partial skull, preserving roughly two-thirds of the cranium caudal to the posterior border of the orbits (Figure 18B, C). The right side is damaged up to the medial wall of the left supratemporal fenestra. This, likewise, provides a clear view of elements of the chondrocranium. The foramen magnum is well preserved in this individual and was partially prepared out to provide a view of the otic capsules and metotic fissure. UA 8766 is the least complete of the recovered skull material. Like FMNH PR 2299, it is a partial cranium consisting of the occipital and lateral chondrocranial elements, some of the dermal roofing bones, and the posterior-most pterygoid. UA 8775 comprises much of the posterior skull (Figure 18A). The frontal and most of the skull table is present. The occiput is well preserved, detailing the cranial nerve and carotid foramina. The left quadrate and much of the basisphenoid is present and largely complete. Although, the braincase and inner ear is predominately absent, the left and right laterosphenoids are preserved and nearly complete. UA 8775 preserves portions of the posterior end of the pterygoid and internal choana. Also, it is one of the few skulls that have the ventral aspect of the mandibular portion of the quadrate exposed. Premaxilla There are five teeth present in the premaxilla with the fourth being the largest and the first and fifth the smallest. The external narial fenestra faces anterolaterally. The posterolateral process of the premaxilla divides the maxilla from the nasal anteriorly (Figure 9A, B). The maxilla curves away ventrolaterally to accommodate a hypertrophied dentary tooth, while the nasals show little to no constriction. The posterior margin is rounded and smooth with a narrow contact with the maxilla. Dorsally, this contact becomes more extensive as evidenced by a substantial contact face beginning just prior to the posterolateral process. Also seen on the posterior margin is a small depression corresponding to the premaxilla/maxilla foramen, similar to that in A. patagonicus and A. gomesii. There is a foramen in the posteroventral corner between the fourth and fifth premaxillary teeth (Figure 20). This foramen is associated with a ventrally directed groove. This appears similar to a foramen present in A. patagonicus, which Ortega et al. (2000) suggested as the anterior end of the lacrimal duct. The two foramina, however, are not topographically equivalent as the foramen in A. patagonicus resides between the premaxilla and the maxilla. The internarial bar is largely formed by the nasals. If, or to what extent, the premaxillae participated in the formation of the bar cannot be determined in any of the specimens of the A. tsangatsangana. Maxilla A nearly complete maxilla is preserved in UA 8720 with partial maxillae preserved in specimen FMNH PR 2297 and FMNH PR The facial portion of the maxilla is nearly vertically oriented with only the dorsal-most portion medially. This, combined with horizontal nasals, forms a rectangular/trapezoidal snout. The alveolar margin is slightly festooned dorsoventrally, reaching its most ventral position at the level of the enlarged third maxillary tooth and its most dorsal position at roughly the position of the fourth maxillary tooth (Figure 21). This feature is shared with other Araripesuchus species and is paralleled in some derived neosuchians. The anterior margin of the junction with the premaxilla is concave. The dorsal portion of the

12 New Araripesuchus from Madagascar 265 maxilla extends anteriorly farther than the ventral margin. A. gomesii differs from this condition the anterior-most portion of the maxilla is ventral as opposed to dorsal (Figure 21). Dorsally, the ascending process of the maxilla contacts the lacrimal and the prefrontal in a broad overlapping suture, thereby separating the nasals from contacting the lacrimal. This differs from the condition in A. gomesii and A. patagonicus where the lacrimal and prefrontal are of roughly equal size and wedge-shaped. The maxilla lacks a contact with the prefrontal due to the nasals contact with the lacrimal in this taxon. The maxilla lacks the internal struts and sinuses found in living crocodylians (Parsons 1970). Posterior to the third maxillary tooth, however, the palatal processes bear a complex series of intersecting ridges and depressions. These ridges are very thin and are only preserved on one maxilla fragment (FMNH PR 2321, Figure 22A). Clark (1986) described similar ridges in Protosuchus, suggesting that they may correspond to the location of the nasal conchae. In contrast, the ventral surface of the palatal processes of the maxilla are simple and unsculpted (Figure 22B). In all Araripesuchus species the nasals are excluded from the participation in the antorbital fenestra. The maxilla forms the anterior half of the nearly circular antorbital fenestra. Posteriorly, the maxilla is overlapped by the anterior process of the jugal. The lateral surface bears a mildly sculpted texture and a row of moderately large foramina just above the alveolar margin (Figure 21). The maxilla held at least eight teeth. The first three teeth are conical with the third tooth being the largest. After the third tooth, the maxillary teeth become spatulate in shape. The tooth row ends just prior to the posterior margin of the antorbital fenestra. Nasal The nasal is long and transversely narrow. Anteriorly, it forms the posterodorsal margin of the external narial fenestra. It widens slightly posteriorly and sutures transversely with the frontal and diagonally with the prefrontal. These sutures are not zigzag as in A. gomesii but rather linear in form. The dorsal surface bears sculpturing composed of shallow longitudinal grooves and, anteriorly, small foramina. Lacrimal The lacrimal has an inverted L-shape in lateral view. The lacrimal forms the posterior and posterodorsal surface of the antorbital fossa. It is only exposed laterally there is no dorsal exposure even under the maxilla. The posterior-most portion forms the preorbital bar, which is surficial but has a small lamina extending into the antorbital fenestra. The remainder of the lacrimal extends forward just past the midpoint of the antorbital fenestra and continues unexposed under the maxilla just past the anterior margin of the fenestra (Figure 23). The maxilla is thin in this overlap region. The lacrimal is narrow throughout, and forms an extensive contact with the prefrontal along its entire length, anteriorly under the maxilla and posteriorly along the prefrontal bar. The lacrimal duct is very large. Its posterior opening is roughly one-third the size of the lacrimal bone. The duct runs dorsally in the lacrimal and narrows anteriorly. The duct opens anteriorly and medially at the end of the lacrimal under the maxilla (Figure 23). The descending pillar of the lacrimal is robust throughout. Ventrally, the pillar expands posteriorly forming the anteroventral edge of the orbit. The ventral margin of the lacrimal is overlapped by the maxilla and jugal. Unlike A. gomesii, the posterior lateral edge of the lacrimal in A. tsangatsangana lacks a contact face for the palpebral. Prefrontal Anteriorly, the prefrontal is broad and comprises, almost solely, the dorsal pre-orbital area as well as the anterior wall of the orbit. It has a short anterior process that divides the posterior regions of the maxilla and nasal. This process, coupled with a maxilla that extends dorsally over the antorbital fenestra, completely separates the lacrimal from contact with the nasal. This is unlike A. gomesii (AMNH 24450), which has a wedge-like lacrimal and prefrontal, both of which contact the nasal. Contrary to Ortega et al. (2000), the naso-prefrontal-lacrimal contact in A. patagonicus does not differ much from A. gomesii (what difference is present is unlike that noted by authors) (Figure 4). The relative proportions of the three bones are similar between the two taxa, however, lacrimo-nasal contact is shorter in A. patagonicus than in A. gomesii. Ortega et al. s observation that a large difference exists is due to a misinterpretation of the extent of the prefrontal. The structure they identified as the prefrontal was only the posterior process they attributed the remainder of the bone to the lacrimal while mistaking the true contact between the lacrimal and prefrontal as a crack or ridge (Ortega et al. 2000: fig. 5). Therefore, the contact between the prefrontal and nasal is not short in A. patagonicus, neither is the lacrimo-nasal suture very long. In fact, given the preservation of the holotype (MUCPV 269) the presence of a contact between the lacrimal and nasal is ambiguous (Figure 4). Only on close examination of the rostrum of MUCPV 268 does a contact between the two elements become apparent.

13 266 A. H. Turner

14 Figure 9. UA 8720, Araripesuchus tsangatsangana. Skull in dorsal view (A, photograph; B, line interpretation of cranial sutures). Scale ¼ 1 cm. (Photo

15 268 A. H. Turner

16 Figure 10. UA 8720, Araripesuchus tsangatsangana. Skull in right lateral view (A, photograph; B, line interpretation of cranial sutures). Scale ¼ 1 cm. (Ph

17 270 A. H. Turner Figure 11. UA 8720, Araripesuchus tsangatsangana. Skull in ventral view. Scale ¼ 1 cm. (Photograph by C. Leonard.)

18 New Araripesuchus from Madagascar 271 Figure 12. UA 8720, Araripesuchus tsangatsangana. Skull in anterior view. Scale ¼ 1 cm. (Photograph by C. Leonard.) Figure 13. UA 8720, Araripesuchus tsangatsangana. Skull in left lateral view. Scale ¼ 1 cm. (Photograph by C. Leonard.)

19 272 A. H. Turner

20 Figure 14. FMNH PR 2297, Araripesuchus tsangatsangana. Skull in dorsal view (A, photograph; B, line interpretation of cranial sutures). Scale ¼ 1 cm. (P

21 274 A. H. Turner

22 Figure 15. FMNH PR 2297, Araripesuchus tsangatsangana. Skull in right lateral view (A, photograph; B, line interpretation of cranial sutures). Scale ¼ 1 cm

23 276 A. H. Turner Figure 16. FMNH PR 2297, Araripesuchus tsangatsangana. Skull in ventral view. Scale ¼ 1 cm. (Photograph by C. Leonard.)

24 New Araripesuchus from Madagascar 277 Figure 17. FMNH PR 2297, Araripesuchus tsangatsangana. Skull in left lateral view. Scale ¼ 1 cm. (Photograph by C. Leonard.) The dorsal surface of the prefrontal in A. tsangatsangana has a longitudinal ridge running near the midline of the bone. Medial to this ridge, the dorsal surface is sculpted with fine longitudinal grooves. Lateral to the ridge the dorsal surface is smooth. The prefrontal has a long posterior process that extends nearly midway along the dorsal margin of the orbit, where it is thick and triangular in crosssection. The frontal/prefrontal suture is complex. The frontal has a ventrolaterally directed flange upon which most of the prefrontal rests. Ventrally, this flange abuts against a medially directed process from the ventral surface of the prefrontal. This forms a pseudo-tongue-in-groove suture between the prefrontal/frontal (Figure 24). Beginning just prior to the orbit, the prefrontal becomes very pneumatic with the posterior process and the prefrontal pillar completely hollow (prefrontal recess sensu Witmer 1995; Figure 25). This condition is generally similar to that found in Alligator mississippiensis and Alligator mefferdi (Brochu 1999), although it should be noted that shape and extent of pneumaticity is variable within alligatorids. In A. tsangatsangana, the prefrontal recess is smaller and the prefrontal pillars are much narrower and caudally slanted, lacking the opening on the medial process of the pillar (Figure 26). The lack of the opening could be an artifact of preservation. The left prefrontal pillar is slightly distorted medially and the right prefrontal pillar is broken and displaced midway along its length by the right palpebral bone, which is preserved lodged within the orbital cavity. Nevertheless, it is clear that the prefrontal pillar has a dorsal process that flares medially, as well as a ventral flaring at its contact with the palatine and pterygoid. This is similar to the condition found in A. gomesii (AMNH 24450). Jugal The jugal is triradiate and shows a distinct lateral bowing (Figure 27). Anteriorly, the jugal is dorsoventrally broad and overlaps the maxilla and lacrimal. Although it is poorly preserved, the jugal, like other crocodylomorphs, does not participate in the antorbital fenestra. Its posterior, or infratemporal process, is slender and tapers to a point in its overlapping contact with the lateral surface of the quadratojugal. The dorsal projection of the jugal is slender and rod-like. It is directed obliquely inward to meet the parietal and is also slanted posteriorly. Anteriorly, the lateral surface bears a longitudinal ridge that, posteriorly, becomes the ventral surface as the jugal rotates ventromedially (Figure 27B). This gives most of the jugal anterior to the post-orbital bar a triangular cross-section. The lateral and ventral surfaces have an alveolar ornamentation (longitudinal grooves and pits). Also, there is a small siphonal foramen at the caudal base of the postorbital bar (Figure 27A). Frontal The frontal is undivided. The dorsal surface is transversely flat and does not narrow between the orbits. Anteriorly, the frontal meets the nasals in a nearly transverse suture with the anterior most tips of the frontal continuing under the nasals. The bone is bordered anterolaterally by the prefrontals. It meets the parietal posteriorly between the anterior most ends

25 278 A. H. Turner Figure 19. Reconstruction of the skull of Araripesuchus tsangatsangana in left lateral view. (Original illustration by Luci Betti Nash.) Figure 20. UA 8720, Araripesuchus tsangatsangana. Close-up of left premaxilla/ maxilla contact, showing detail of the premaxilla and the suture with the maxilla. Scale ¼ 1cm. (Photograph by C. Leonard.) large recess that runs underneath the dorsal ridge for half the length of the frontal. Posteriorly, three chambers open and continue to run posteriorly with the middle opening into a number of chambers, the Figure 18. Skulls of Araripesuchus tsangatsangana in posterior view. A, UA B, FMNH PR C, Line interpretation of cranial sutures in FMNH PR Scale ¼ 1 cm. (Photographs by C. Leonard.) of the supratemporal fenestrae the frontal just entering into the supratemporal fossa (Figure 28). The frontal has a very short contact with the postorbital. Internally, the frontal is marked with numerous cavities (Figure 29). Anteriorly, there is a Figure 21. FMNH PR 2321, Araripesuchus tsangatsangana. Lateral view of isolated maxilla, showing festooned ventral margin and foramina above the alveolar margin. Scale ¼ 1 cm. (Photograph by C. Leonard.)

26 New Araripesuchus from Madagascar 279 Figure 22. FMNH PR 2321, Araripesuchus tsangatsangana. A, Dorsal view of the palatal lamina, showing internal ridges and depressions. B, Palatal view, showing smooth surface. Scale ¼ 1 cm. (Photograph by C. Leonard.) lateral two continuing and ending in large recesses posterior to the orbit and underlying the postorbital frontal parietal contact. Ventrally, a small ridge runs the midline of the bone along the anterior half. The lateral processes, with which the prefrontals suture, are continuous with well-developed sharply ridged cristae cranii. These border a median channel for the olfactory tracts (Figure 29B). The laterosphenoids ascend and contact the posteromedial portion of the cristae. Parietal The parietal is undivided and forms the posterior border of the skull table, but does not continue onto the occipital surface (Figure 28). The posterior edge is straight to slightly concave with a small median projection corresponding to the dorsal edge of the supraoccipital crest. The suture between the parietal and the supraoccipital is indistinct but no postparietal is present. Posterolaterally, the parietal meets the squamosals. The parietal is not strongly constricted between the supratemporal fenestrae. The parietal forms the medial wall of the supratemporal fenestrae and borders the foramen for the temporo-orbital artery. Contact between the parietal and postorbital is restricted to within the supratemporal fenestra. Also, this bone lacks recesses like those of the frontal. The crista cranii parietalis are not as extensive as in Alligator (Figure 30). They slant lateroventrally gradually and contact the laterosphenoid high within the supratemporal fenestra (2: CorFlip: 314). Postorbital The postorbital has a narrow dorsal surface. The dorsal surface is flat, bearing an overall gently convex anterolateral border with the anterolateral corner possessing a slight concave indentation (Figure 28). This indented corner possesses a lower shelf on which the posterior palpebral rests. This is seen in A. gomesii (AMNH 24450), A. patagonicus (Ortega et al. 2000), Notosuchus (pers. obs.; MACN RN 1037, 1040, 1041), Malawisuchus (Gomani 1997) and peirosaurids (Gasparini et al. 1991). Posteriorly, the postorbital extends nearly midway along the length of the supratemporal fenestra. It forms the anterolateral corner of the fenestra and broadly overlaps the squamosal. A thin anteroposteriorly broad lamina descends and bifurcates ventrally with the posterior portion of the lamina, contacting the quadrate broadly the posteroventral portion contacting the narrow ascending process of the quadratojugal in a V -shaped suture and the anteroventral portion forming the dorsal-most portion of the rod-like postorbital bar. The postorbital bar is inset from the skull table and the lateral side of the jugal. The postorbital meets the frontal medially along a parasagittal contact, and it contacts a very small portion of the parietal within the supratemporal fossa.

27 280 A. H. Turner Figure 23. UA 8720, Araripesuchus tsangatsangana. Coronal CT slices through the posterior portion of the rostrum, showing internal lacrimal and lacrimal recess morphology. Quadratojugal The quadratojugal is preserved only in FMNH PR The quadratojugal extends anteriorly to meet the postorbital bar. The suture with the postorbital is V -shaped, with the dorsal extent of the V unclear due to fracturing and obscuring matrix (Figure 31). A similar condition is found in A. gomesii. Posteriorly, the quadratojugal overlaps the quadrate laterally and has moderate lateral exposure. The quadratojugal is narrow at the infratemporal fenestra and forms the posteroventral margin of the fenestra. The overlapping jugal, however, obscures most of the ventral margin. The quadratojugal is visible dorsally and does not participate in the lateral hemicondyle of the quadrate (similar to A. patagonicus, but contrasting that of A. gomesii). The surface of the quadratojugal is smooth. Figure 24. UA 8720, Araripesuchus tsangatsangana. Coronal CT section through the anterior border of orbits, showing contact between prefrontals and frontal. Squamosal This is a triradiate bone that forms the posterolateral corner of the skull table. The dorsal surface slopes

28 New Araripesuchus from Madagascar 281 Figure 25. Detail and comparison of prefrontal recesses in UA 8720 (Araripesuchus tsangatsangana A, B) and TMM m-7487 (Alligator mississippiensis C, D) as seen in coronal slices through each skull. very gently laterally. The squamosal extends anteriorly under the postorbital but does not reach the postorbital bar (similar to that seen in Notosuchus). The squamosal is broad lateral to the supratemporal fenestra. Medially, the squamosal contacts the parietal in a broad suture and comprises the lateral wall of the temporo-orbital artery foramen. The lateral surface of the squamosal bares a fairly well developed groove for the attachment of the external ear musculature. The occipital portion of the squamosal is concave, and the posterolateral process is very long and bends downwards overhanging the otic recess and forming the paroccipital process. The squamosal comprises one-third of the skull table width. The posterolateral lobe is completely hollow, formed by a single chamber and there is a long cylindrical chamber that runs the length of the paroccipital process (Figure 32). Quadrate The quadrate is dorsolaterally inclined as in most basal mesoeucrocodylians. Internally, the quadrate extends horizontally to contact the basioccipital, basisphenoid, and laterosphenoid. The quadrate is not developed ventrally at this contact as it is in crocodylians. Medially, the quadrate contacts the

29 282 A. H. Turner Figure 26. Sagittal CT section through left prefrontal recess in UA 8720 (Araripesuchus tsangatsangana A) and TMM m-7487 (Alligator mississippiensis B). otoccipital (Figure 34). Dorsal to this contact, the squamosal overlies the quadrate and otoccipital forming the cranioquadrate canal. The dorsal surface bears a large otic incisure. Just anterior to the otic incisure the quadrate bears a small preotic siphonium. Within the otic recess surrounding the two foramina, the quadrate has a shallow depression, however, no ridge is present as it is in A. gomesii (Price 1959; AMNH 24450) (Figures 31, 33). Posteriorly, the mandibular condyles are directed almost completely ventrally (Figure 18A, B). The lateral hemicondyle is nearly spherical in aspect and the medial hemicondyle is very reduced and lateromedially narrow. The articular surface slants medioventrally. The posterior surface of the quadrate bears a large triangular depression formed from the dorsal surface of the quadrate, the terminus of the paroccipital process, and a distinct medial ridge running from the medial condyle dorsally to the paroccipital process. This medial condylar ridge marks the lateral border of the foramen aërum, which is bounded solely by the quadrate. The paroccipital process is large and formed from the posterior lobe of the squamosal. No ascending lamina from the quadrate is present (unlike Alligator) and therefore the quadrate contributes only to the ventral surface (Figure 34). Supraoccipital This bone is not exposed dorsally. In posterior view it is much wider than tall (Figure 18). The ventral border is Figure 27. UA 8752, Araripesuchus tsangatsangana. A, Medial view of the jugal. B, Lateral view of jugal. Scale ¼ 1 cm. (Photograph by C. Leonard.)

30 New Araripesuchus from Madagascar 283 Figure 28. FMNH PR 2299, Araripesuchus tsangatsangana. Dorsal view of skull table showing interpretation of sutures. Scale ¼ 1 cm. (Photograph by C. Leonard.) not as strongly triangular in shape as in most eusuchians. The supraoccipital of A. tsangatsangana has a more broad angularity with a very sharp downturn right at the midline, forming a small V -shape. Dorsolaterally, rudiments of the post-temporal fenestrae are present. Medial to the post-temporal fenestrae, postoccipital processes protrude. These are very reduced as in the other Araripesuchus species. The dorsal surface of the process faces dorsolaterally as in most eusuchians (in Notosuchus and Comahuesuchus this surface faces dorsally). The occipital surface is depressed on either side of the midline and a welldeveloped nuchal crest is present. It can be seen in CT imagery that the supraoccipital does not extend anteriorly as much as in Alligator, though it does possess a large mastoid antrum connecting the middle ear regions through a transverse canal (Figure 35). Exoccipital The exoccipitals form most of the occipital surface (see below Figures 18, 28). The two bones meet above the foramen magnum, where they form a small posterior process on which the proatlas articulates. The exoccipitals, and the occiput in general, are divided by a transverse crest extending between the quadrates above the foramen magnum. This ridge is very pronounced in A. tsangatsangana and A. patagonicus. It is less developed in A. gomesii (AMNH 22450) and cannot be observed in Araripesuchus buitreraensis from Argentina (Pol and Apesteguía 2005). Figure 29. UA 8720, Araripesuchus tsangatsangana. Coronal CT sections showing frontal recesses. A, Anterior section showing the prominent medium frontal recess (mfr). B, CT section midway through orbits showing the three frontal recesses and distinct cristae cranii (ccrf). C, Posterior section showing numerous recesses within the frontal. A large ventrolateral process is present and forms the medial wall of the cranioquadrate canal (laterally enclosed by quadrate and squamosal) and extends ventrally to its contact with the basisphenoid. This

31 284 A. H. Turner Figure 30. Comparison of parietal and crista cranii parietalis morphology between FMNH PR 2297 (Araripesuchus tsangatsangana A) and TMM m-7487 (Alligator mississippiensis B). contact is at the level of the base of the basioccipital (Figure 34). The exoccipitals form the posterior parts of the lateral walls of the cerebral cavity. Anteromedially, the exoccipital (fused to opisthotic) forms the posteroventral portion of the bulla tympani (cochlear prominence) as it does in crocodylians (Figure 34). The remnant of the metotic fissure, which allows passage of the IX and X nerves, is poorly preserved but distinguishable (also see Figure 33A). It is unlike adults of modern species in that the metotic fissure has a more posterodorsal aspect. At least one, and perhaps a second, medial hypoglossal (XII) foramina are present. Halfway Figure 31. FMNH PR 2298, Araripesuchus tsangatsangana. Right quadratojugal (highlighted in yellow), showing V -shaped contact with postorbital and failure to form a portion of the mandibular condyle. Scale ¼ 1 cm. (Photograph by C. Leonard.) Figure 32. FMNH PR 2297, Araripesuchus tsangatsangana. Coronal CT section showing recess in the posterolateral lobe of the squamosal.

32 New Araripesuchus from Madagascar 285 Figure 33. FMNH PR 2297, Araripesuchus tsangatsangana. CT imagery of various braincase morphology including otic capsule and Eustachian sinuses. A and C, Coronal CT sections through the posterior right quadrate of braincase. B and D, Sagittal CT sections through the braincase right of the midline. between the occipital condyle and the quadrate a large foramen vagi is present and just ventromedial to this there is a slightly smaller posterior carotid foramen. This allows the internal carotid artery to pass dorsomedially into the middle ear cavity. The dorsal-most portion of this tract, however, is not preserved in FMNH PR Basioccipital The basioccipital forms almost all of the small occipital condyle that is slightly developed ventrally. It does not have the slight central excavation seen in most eusuchians (Figure 18). The occipital condyle does have a large antrum and the anterior portion of the basioccipital holds the posterior channel for the median Eustachian tube (Figure 36C). Basal tubera are not present, but a well-developed medial crest is present, which serves as attachment for the Mahajangasuchus basioccipitovertebralis and M. occipitotransversalis profundus (Fürbringer 1876). The ventral tip of the basioccipital forms a small notch that roofs the entrance to the small median Eustachian opening. Two small parasagittal crests are present alongside the median crest. The lateral Eustachian foramina are not exposed on FMNH PR 2297, but are

33 286 A. H. Turner Figure 34. FMNH PR 2299, Araripesuchus tsangatsangana. Ventrolateral view of the occiput, showing detail of the right otic capsule. Scale ¼ 1 cm. (Photograph by C. Leonard.) large and clearly present in CT data (2: CorFlip: ; Figure 35). The basioccipital forms the posterior part of the floor of the cerebral cavity. the basisphenoid or of the area surrounding the basisphenoid rostrum. Contrast between bone and matrix is poor within the basisphenoid in FMNH PR 2297, but a structure corresponding to the anterior channel for the median Eustachian tube appears to be preserved (Figure 33). The anterior extent of this channel is not well defined and the anterior carotid foramina are not preserved. Moving laterally, especially on the left side, the anterior and posterior channels of the median Eustachian tube open into a large rhomboid sinus (Figures 33, 36). Dorsal to the rhomboid sinus the metotic fissure is seen dividing the opisthotic from the basioccipital. Prootic and opisthotic It is unclear whether the prootic is visible on the lateral side of the braincase. Internally, it forms the anterior portion of the bulla tympani (cochlear prominence); see FMNH PR 2299, CT scan 2: CorFlip: , and Figure 35. Neither in the specimen nor the CT data are any anteroventral openings for the VIII and VII nerves visible. In both FMNH PR 2299 and CT scans, however, the incision for a branch of the VIII can been seen on the posterior margin of the prootic ventral to the bulla tympani (2: CorFlip: ; Figure 35). The prootic contains the ventral portion of the anterior semicircular canal and the anterior half of the lateral semicircular canal, although the lateral semicircular canal is very poorly preserved. The opisthotic is generally well-preserved in FMNH PR 2297 but its exact suture with the exoccipital is not distinguishable in CT data. The opisthotic forms the posteroventral border of the tympanic bulla, delineates the dorsal border of the metotic fissure, and forms the dorsal wall of the perilymphantic foramen. The anterior portion of the lateral semicircular canal is preserved and located within the opisthotic. Basisphenoid The basisphenoid has a large posteroventral exposure, exhibiting very little antero-posterior compression (verticalization). Posterodorsally, the basisphenoid shares a broad suture with the exoccipital. The basisphenoid contacts the basioccipital medially, the quadrate laterally and the pterygoid lateroventrally. The ventral contact with the pterygoid is marked by a narrow transverse furrow. The external surface is marked by two parasagittal ridges like A. gomesii (AMNH 22450) and A. patagonicus (MUCPV 269), the ventral of the two corresponding to ridge B of Iordansky (1973). A basisphenoid rostrum is present but poorly preserved in all specimens. Because of the poor preservation in the two skulls for which there is CT data, little can be said of the internal morphology of Laterosphenoid The laterosphenoid forms the anterolateral wall of the braincase. In both specimens where the laterosphenoid is exposed, the posterior-most portion is not well preserved and therefore does not show contact with the prootic or quadrate. CT data (2: CorFlip: ), however, very poorly shows the contact between the laterosphenoid and quadrate. This contact can be seen very clearly in A. gomesii. Dorsally, the laterosphenoid sutures with the frontal and parietal. The capitate process contacts the postorbital anterodorsally. There it rests within a shallow ventral fossa and, ventral to this, sutures with the basisphenoid. The anterior tips of the laterosphenoids converge at the midline but do not contact each other, similar to A. gomesii. Notches for the exit of cranial nerves II

34 New Araripesuchus from Madagascar 287 Figure 35. FMNH PR 2297, Araripesuchus tsangatsangana. Coronal CT section of skull through braincase showing median and lateral Eustachian tubes. and III are difficult to discern, but appear to be present along the anterior edge, as in A. gomesii and modern crocodylians. A foramen for cranial nerve IV cannot be discerned from the fossil or CT data. The laterosphenoid forms the anterior branch (supplying the M. levator bulbi) pass anteriorly from the foramen ovale edge of the trigeminal opening (foramen ovale) (Figure 37A, C). A laterosphenoid bridge may be present in A. tsangatsangana (FMNH PR 2298) and, although fractured, a structure corresponding to this may be evident in CT imagery (2: CorFlip: ). This bridge is present in crocodylians but is not present in the early eusuchian Hylaeochampsa (Clark and Norell 1992). In the crown group, the ophthalmic branch of the trigeminal nerve and a small offshoot of its mandibular between the bridge and the main body of the laterosphenoid (Iordansky 1973). The walls of the laterosphenoid that are exposed suggest that a bridge is, in fact, not present in A. tsangatsangana (Figure 37). A shallow groove dorsal to the foramen ovale corresponds to the path of the trigeminal nerve s ophthalmic branch and the branch supplying the M. levator bulbi (Clark et al. 1993). If the ophthalmic branch is, indeed, traversing across the lateral wall of laterosphenoid in the area indicated by the groove (gov, Figure 37) then based on the principles of connectivity and character congruence, no bridge homologous to that seen in crocodylians is present in the A. tsangatsangana. Palatine The palatines are poorly preserved or not present in most of the specimens. FMNH PR 2297 preserves the caudal-most portion of the palatines and the anterior border of the internal choana (Figure 38). A distinct choanal septum is present. It is narrow and bears no other distinctive features. CT data further reveals the presence of the palatal processes of the maxillae and with their shape, a general outline of the palatines can be inferred. The palatines are somewhat narrow with subparallel lateral margins. They extend rostrally between the maxillae 1 or 2 cm beyond the anterior border of the suborbital fenestra. This is similar to the condition in peirosaurids but different from that of Notosuchus (MACN RN 1037, 1040, 1041) or Comahuesuchus (MACN P6131) the palatines do not extend rostrally very far in these taxa. No palatal fenestra is present. Like A. gomesii and A. patagonicus, a small portion of the palatines extends laterally forming a portion of the anterior border of the suborbital fenestra. Nonetheless, the dorsal laminae of the palatines are preserved in both UA 8720 and FMNH PR 2297 and are clearly seen in the CT scans (Figure 25B). These laminae are relatively tall and form the lateral walls of the nasal passage. Ectopterygoid The ectopterygoids are only partially preserved in FMNH PR 2297 (Figure 39A). CT scans

35 288 A. H. Turner Figure 36. FMNH PR 2297, Araripesuchus tsangatsangana. Horizontal CT sections (A, B, C) of skull through braincase showing median and lateral Eustachian tubes, posterior carotid foramen, and basioccipital antrum. (2: CorFlip: ) reveal a short, moderately robust ectopterygoid (Figure 39B, C). Also revealed in the scans is a small recess in its ventral portion. This bone forms the lateral edge of the pterygoidal flange, does not overlap the ventral surface of the pterygoid to any significant extent, and lacks any significant posterior process. The ectopterygoid extends anterolaterally to contact the jugal and the posterior-most portion of the maxilla. The bone appears to not extend posterior enough to contact the postorbital bar (see 2:CorFlip: 296). Pterygoid The pterygoid plate has a broad flat ventral surface that faces anteriorly. No good exposure of the ventral surface is preserved so the presence or absence of a sagittal suture line or a midline depression posterior to the choana (as seen in A. patagonicus and A. gomesii) cannot be determined. FMNH PR 2299 possesses a very well preserved dorsal surface (Figure 40). The dorsal surface of A. patagonicus was described as flat rather than concave (Ortega et al. 2000: 64). In my examination of both MUC PV 268 and MUC PV 269, however, this dorsal surface was not exposed. The pterygoid in the A. tsangatsangana (FMNH PR 2298) has a dorsal process that contacts the laterosphenoid (forming the ventral border of the foramen ovale), the quadrate, and posteriorly, the basisphenoid. The dorsal process is transversely narrow with a distinct anterior and posterior face. This distinction continues on the long transverse process, forming a ridge (rather than a flat surface) with the caudal side of the ridge facing posteriorly and the rostral side facing dorsally, continuous with the anterior (palatal) process of the pterygoid. This anterior process is broad posteriorly and narrows as it extends forward along the midline. The ventral surface of this anterior extension forms a pair of lateroventrally open troughs. These form the posterior boundary and the dorsal enclosure of the internal choanae. This anterior process caps the posterior

36 New Araripesuchus from Madagascar 289 Figure 38. FMNH PR 2297, Araripesuchus tsangatsangana. Threedimensional CT reconstruction of the palate with the surrounding matrix digitally removed. Only the caudal portions of the palatines are preserved as they form the anterior border of the internal choana. Figure 37. Details of laterosphenoid in Araripesuchus tsangatsangana. A, Right lateral view of FMNH PR 2299, showing relationships between laterosphenoid, basisphenoid, parietal, and foramen ovale, as well as features possibly associate with ophthalmic artery and nerve. B, Left lateral view of UA 8775, showing possible groove for ophthalmic nerve and details of capitate process. C, Left laterosphenoid of FMNH PR Scale ¼ 1 cm. (Photographs by C. Leonard.) portion of the dorsal processes of the palatines. Unlike modern crocodylians, the anterior process of the pterygoid sits high on the palatines and has a distinct crest on the dorsolateral borders. The pterygoid of modern species sits more ventrally, resting between the dorsal palatal processes not capping them as in A. tsangatsangana. The pterygoid contacts the prefrontal pillar, but a bulla is lacking on the dorsal surface. It has been noted in A. gomesii and A. patagonicus that the pterygoid possesses a T shaped spine that divides the internal choanae (Ortega et al. 2000). This spine can be seen in CT data (1: CorFlip: ; fig. 25) and it completely divides the nasopharyngeal passage. In this respect, the spine would better be characterized as a septum. In A. gomesii and A. patagonicus, the septum separates the posterior-most ends of the palatines on the secondary palate. It is unclear, however, if this separation is the result of preservation or slight disarticulation of the palatines. Vomer The vomers are badly broken but identifiable in CT data. These are long and narrow and rest within the

37 290 A. H. Turner Figure 39. FMNH PR 2297, Araripesuchus tsangatsangana. Morphology of ectopterygoid, as shown in a photograph of dorsal surface (A); a coronal slice through CT reconstructed skull (B); and (C) a three-dimensional CT reconstruction of the left and right ectopterygoids with the surrounding matrix digitally removed. The elements are incomplete with the extent of their preservation highlighted in green. In C, scale ¼ 1 cm. (Photograph by C. Leonard.) palatal processes of the maxillae and the palatines. They are not exposed on the palate as in Simosuchus clarki (Buckley et al. 2000). Dentary The dentary is a very characteristic element in A. tsangatsangana. The first third of the dentary is dorsoventrally flat and moderately broad mediolaterally, with the alveolar margin from alveoli 1 11 situated lower to the remaining alveoli, and the first nine teeth mildly directed anteriorly with slight procumbency. Taken together, this forms a spatulate anterior mandibular margin. This morphology diminishes posteriorly, as the alveoli posterior to the tenth alveolus are directed more or less vertically. In total, the dentary has sixteen alveoli. A series of small neurovascular foramina form a row along the lateral dentary ventral to the alveoli. Posterior to alveolus 15, the foramina are replaced by a narrow groove running parallel to the tooth row and ceasing below the penultimate dentary tooth (Figure 41A, B). Laterally, there is a subtle indentation at the ninth alveolus to accommodate the enlarged third maxillary tooth. The dentary gradually slopes dorsally after the tenth alveolus. The ventral surface bears small pits, while the posterior third is relatively smooth and relatively unornamented. This general dental morphology is similar to that seen in A. patagonicus, A. gomesii and A. wegeneri.

38 New Araripesuchus from Madagascar 291 Figure 40. FMNH PR 2298, Araripesuchus tsangatsangana. Left lateral view of dorsal surface of pterygoid. The anterior process is deflected dorsally thereby displacing the true contact between the pterygoid and laterosphenoid. Scale ¼ 1cm. (Photograph by C. Leonard.) Ortega et al. (2000: 64) described the dentary of A. patagonicus as having a convex lateral profile that is dorsal and ventrally deflected. This is perhaps a bit of an oversimplification of the morphology. In reality, only the middle third of the dentary displays anything that could be described as convex. The anterior third, like in A. gomesii, A. wegeneri and A. tsangatsangana, is nearly completely dorsoventrally flattened and bears little in the way of a dorsally deflected lamina (Figure 41B, C). Conversely, the posterior third of the dentary is thin in all Araripesuchus taxa and are vertically oriented with little to no ventro-medial lamina (Figure 41A, D). The posterior margin is thin and overlaps the surangular laterally, forming the upper margin of the external mandibular fenestra (Figure 42A). Ventrally, the dentary overlaps the angular but does not extend beneath the external mandibular fenestra. Contra the coding of Pol and Norell (2004), this same morphology is seen in both A. patagonicus and A. gomesii. In medial view, the Meckelian groove tapers anteriorly Figure 41. Dentary morphology in Araripesuchus tsangatsangana. A, Dorsal view of dentary FMNH PR B, Right lateral view of FMNH PR 2318, showing the complex outline of the dentary. C, Coronal section through anterior rostrum of UA 8720, showing the dorsoventrally flat symphyseal region. D, Coronal section midway through orbits, showing the vertical dentary possessing little or no ventromedial lamina. In A and B, scale ¼ 1 cm. (Photographs by C. Leonard.)

39 292 A. H. Turner Figure 42. Posterior mandible morphology. A, Lateral view of left dentary and angular of FMNH PR 2299, showing the dentary overlapping the angular. B, Dorsal view of the surangular of FMNH PR 2299, showing the small dorsally projecting triangular lamina. C, Medial view of posterior mandible in FMNH PR 2298, showing the triangular lamina for the Cartilago transiliens, the contact between the surangular and angular, and a possible coronoid. Scale ¼ 1 cm. (Photographs by C. Leonard.) to the point below the eighth alveolus, demarcating the splenial contact. A small foramen is present at the anterior terminus of the groove marking the continuation of the Meckelian canal further into the dentary (1: CorFlip: ). The long axis of the symphysis extends anteroposteriorly back to the ninth alveolus. The dentary comprises roughly two-thirds of the length of the symphysis of the mandible (Figure 43A). When articulated, the left and right dentary rami would have formed a V -shape in dorsal view with the symphyseal region lying flat and broad. There is no abrupt constriction of the symphysis as in Notosuchus terrestris (MACN-RN 1037; pers. obs.), and Araripesuchus (AMNH 24450) lacks the deep trough-like symphysis present in the former taxon. Splenial This is a thin, elongate bone that begins at the mandibular symphysis, expanding posteriorly to enclose most of the Meckelian fossa. The splenial is best preserved in FMNH PR 2316, but can also be seen in FMNH PR 2297, CT data of FMNH PR 2297, as well as FMNH PR The splenial takes part in the mandibular symphysis forming a strongly interlocking suture and constituting roughly one-third of the symphyseal length (Figure 43A). This proportion of dentary to splenial at the symphysis is like that found in A. gomesii (Price 1959, Hecht 1991) and A. wegeneri (GDF 700). Ventrally, the splenials taper to a point forming a V -shaped process between the dentaries. This V -shape is like that found in other Araripesuchus as well as Malawisuchus (Gomani 1997), but differs from the U-shaped splenial symphysis seen in Notosuchus (MACN RN1037, 1040, 1041), Comahuesuchus (MACN P6131; MACN N31) and Anatosuchus (MNN GDF603). Posterior to the symphysis, the splenial narrows and forms approximately one-third of the ventral surface of the mandible. In medial view, there is a small posteriorly directed protuberance located at the suture between the two splenial elements in A. tsangatsangana. A large

40 New Araripesuchus from Madagascar 293 Figure 43. UA 8720, Araripesuchus tsangatsangana. A, Ventral view of mandibular symphysis in a three-dimensional CT reconstruction of the skull with the surrounding matrix digitally removed. B and C, Coronal CT sections through snout, showing the splenial/dentary contact and interdigitation of splenials at the symphysis. foramen intermandibularis oralis is present as it is in A. gomesii (Figure 44). Dorsally, the splenial possesses a thin lamina that projects anteriorly a few millimeters and overlaps the dentary at the level of the tenth alveolus. This lamina is continuous with the remainder of the splenial, which thins, taking on a slight convex shape. This forms the medial wall of the mandible and dental alveoli from d12 d16. This slight convexity is unique to A. tsangatsangana A. gomesii and A. patagonicus (to the extent that it is observable in the type specimen) have splenials that lack any convexity. The posterior-most margin of the splenial is not preserved in any of the specimens, so its morphology and contact with the coronoid (which appears not to have been preserved, though see Figure 42) cannot be determined. Hyobranchials The hyoid apparatus in non-crocodylian crocodylomorphs is poorly described. A. gomesii (AMNH 24450) preserve the hyoids, but Hecht (1991) only gave them a cursory mention. Portions of the hyoid apparatus are known from a few crocodylomorphs e.g. Hesperosuchus agilis (Clark et al. 2000), Protosuchus richardsoni (Colbert and Mook 1951), Geosaurus vignaudi (Frey et al. 2002). The elements preserved in A. tsangatsangana are long and slender, likely corresponding to the ceratohyals (Figure 45A, B). In overall shape, the ceratohyals of A. tsangatsangana are similar to A. gomesii. The preserved anterior half of the body of the bone is straight and cylindrical in cross-section. The posterior half curves away from the anterior portion at roughly a 358 angle. This portion of the element becomes compressed and dorsoventrally expanded. CT imagery shows that the ceratohyal of Araripesuchus is hollow throughout its length (Figure 45C). Figure 44. FMNH PR 2316, Araripesuchus tsangatsangana. Lateral view of an isolated right splenial, showing large foramen intermandibularis oralis. Scale ¼ 1 cm. (Photograph by C. Leonard.) Surangular The surangular contacts the posterior process of the dentary above and anterior to the mandibular fenestra. Unlike crocodylians, but similar to other basal

41 294 A. H. Turner Figure 45. FMNH PR 2297, Araripesuchus tsangatsangana. Left and right hyoids, with internal detail from CT imagery. A, Oblique ventral view of left and right hyoid bones. B, Ventrolateral view of hyoids in a three-dimensional CT reconstruction of the skull with the surrounding matrix digitally removed. C, Coronal section showing the hollow interior of the hyoids. In A, scale ¼ 1 cm. (Photograph by C. Leonard.) mesoeucrocodylians, the surangular is overlapped by (as opposed to overlaps) the dentary (Figure 42A). The anteroventral margin of the surangular is concave and forms approximately half of the dorsal and posterior borders of the external mandibular fenestra. The dorsal margin of the surangular is straight with only the posterior-most portion bearing an arch as it descends forming the lateral wall of the mandibular glenoid fossa (Figure 47B). Unlike A. gomesii, the surangular does not form any part of the articular surface. The contact with the angular is straight and parallel with the jaw line. A thin dorsal lamina of the angular, however, overlaps the ventralmost portion of the surangular. The lateral surface of the bone is slightly sculpted. In medial view, there is a shallow fossa for the insertion of the adductor mandibulae externus pars medialis. On the upper surface of the surangular above the external mandibular fenestra, there is a small triangular lamina projecting dorsally. The medial surface of the projection is smooth and it is bordered laterally by a U -shaped groove (Figure 42B, C). This projection is similar to that seen in A. mississippiensis (TMM m-7487), Caiman crocodilus (TMM m-7365) and Paleosuchus trigonatus (FMNH 81980). In these taxa, the projection serves as the contact for the Cartilago transiliens, and the groove is formed from the attachment of the pars superficialis of the adductor mandibular externus (Iordansky 1973). Given the close similarity of shape and location, the structures in A. tsangatsangana likely served the same function as in the modern crocodylians mentioned. The presence of this structure cannot be determined for A. patagonicus and the triangular lamina is not present in A. gomesii (AMNH 24450). Angular The angular consists of a long, acute anterior process that forms the ventral border of the external mandibular fenestra, a dorsally curved posterior portion that overlaps the ventral-most surface of the surangular, and a thin posterior projection that overlies the lateral surface of the retroarticular process. This bone is poorly preserved in most specimens; however, FMNH PR 2297 and FMNH PR 2298 both preserve nearly complete right angulars (Figure 42A and C, respectively) and an isolated angular is known from UA 8754 (Figure 46). The medial surface of the angular is smooth and bears no distinctive features. The dorsal surface of the long anterior process forms the floor of the external mandibular fenestra. This surface comprises a deep groove through which the Meckelian cartilage passes. The lateral surface of the angular is ornamented with small pits, with the pits becoming larger and more closely spaced in larger individuals (see FMNH PR 2297 and FMNH PR 2298). Continuing from the lower margin of the angular is a narrow ridge that

42 New Araripesuchus from Madagascar 295 Figure 46. UA 8754, Araripesuchus tsangatsangana. Lateral view of an isolated left angular. Scale ¼ 1 cm. (Photograph by C. Leonard.) deflects dorsally, dividing the posterior projecting lamina from the dorsally curved portion. This ridge is particularly pronounced in the largest individual (FMNH PR 2299; Figure 42A). The division between the posterior projection overlapping the retroarticular process and the dorsally curved portion is present in the other Araripesuchus species. In the other Araripesuchus species, however, this division is not in the form of a distinct ridge. This ridge is similar to that found in Simosuchus and the eusuchian Mekosuchus, but in A. tsangatsangana it is not nearly as pronounced as in the former taxa. This ridge perhaps provides a large surface area for pterygoideus attachment. Articular The only articular preserved is the left articular in specimen FMNH PR Given that the element is in articulation and partially obscured by rock matrix, its ventral surface and its lateral contact surface with the surangular and angular cannot be seen. The dorsal surface of the articular is complex (Figure 47). The glenoid fossa is roughly ovular with Figure 47. FMNH PR 2297, Araripesuchus tsangatsangana. Morphology of the articular (highlighted in yellow). A, Dorsal view of threedimensional CT reconstruction of the skull with the surrounding matrix digitally removed, showing overall relationship of articular to skull. B, Oblique posterior view of right articular in a three-dimensional CT reconstruction of the skull with the surrounding matrix digitally removed. C, Close-up dorsal view of glenoid fossa and retroarticular process. In C, scale ¼ 1 cm. (Photograph by C. Leonard.)

43 296 A. H. Turner Figure 48. Systematic variation of Araripesuchus retroarticular processes. A, Araripesuchus tsangatsangana (FMNH PR 2297) has a posteriorly projecting process originating from the dorsal part of the mandible. B, Araripesuchus patagonicus (MUCPV 269) has a posteriorly projecting process originating from the ventral part of the mandible. Scale ¼ 1 cm. two broad fossae. These fossae are divided by an anteroposterior ridge with the two fossae on either side corresponding to a hemicondyle of the quadrate. This ridge is not as sharply defined nor as prominent as the ridge present on the articular of Notosuchus terrestris (MACN RN 1037). The two fossae are roughly equal in size and area. Additionally, the two fossae appear nearly twice the area of their respective articulating hemicondyle. The medial fossa slants ventrally at approximately a 458 angle. This slant corresponds to the complementing slant of the medial hemicondyle on the quadrate. The glenoid fossa lacks the posterior glenoid wall present in most eusuchians. The surangular does not form any part of the glenoid fossa, instead forming the lateral wall of the fossa and extending around the glenoid fossa to contact the anterior base of the retroarticular process. The retroarticular process is long and relatively slender. It resembles more closely the retroarticular process of A. gomesii and lacks the extensive medial lamina present on A. patagonicus. Like other Araripesuchus, the process faces dorsally but fails to curve dorsally as the processes of more derived neosuchians do. Unlike other Araripesuchus, the retroarticular process of A. tsangatsangana does not originate from a ventral position, extending posteriorly. Instead, it originates from a more dorsal position, but still retaining the direct posterior extension (Figure 48). A foramen aërum is not preserved on the specimen. Ortega et al. (2000) figured the cranio-mandibular articulation of A. gomesii and A. patagonicus as having a posterior and medial extension, and in text they refer to the articular area as enlarged. They refer to this trait as previously being exclusive to notosuchians, citing Clark et al. (1989) and Gomani (1997). Two points of clarification need to be made. First, the trait to which Clark et al. (1989) and Gomani (1997) refer is an articular allowing longitudinal movement, not simply enlargement. Second, it appears that notosuchian was used by Ortega et al. generally, as that character described by Clark et al. and Gomani is present in only Notosuchus, Malawisuchus and

44 New Araripesuchus from Madagascar 297 Figure 49. Variation of Araripesuchus premaxillary tooth number. A, Araripesuchus tsangatsangana (UA 8720) with five premaxillary teeth. B, Araripesuchus wegeneri (GDF 700) with five premaxillary teeth. C, Araripesuchus gomesii (GDM-DNPM 432-R) with four premaxillary teeth. Chimaerasuchus and was not optimized for a larger clade. It is perhaps arguable that the articular surface of the glenoid fossa is enlarged in Araripesuchus given that the two fossae on which the hemicondyles of the quadrate articulate are indeed larger than the articulating facets of the hemicondyles. However, it does not appear that A. gomesii, A. patagonicus or A. tsangatsangana possess a significant posterior extension of the glenoid articular surface or longitudinal grooves indicative of propalinal motion. Propalinal motion and a long jaw articulation appear to remain a characteristic of a restricted group of notosuchian crocodyliforms. Teeth Although known from other Araripesuchus species, the teeth both dentary and premaxillary/maxillary are poorly described. This is because in most cases the skull and mandible are preserved articulated, obscuring most of the dental detail. Given the disarticulated nature of much of the A. tsangatsangana material and the CT imaging of the two skulls, much more of the dental morphology for the taxon can be described. A. tsangatsangana has five premaxillary teeth (Figure 49A), at least eleven maxillary teeth, and eighteen teeth total in the dentary. Comparatively, A. gomesii has four premaxillary teeth (Figure 49C), eleven maxillary teeth, and an undetermined number of teeth in the dentary; A. patagonicus has four premaxillary, maxillary, and an undetermined number of dentary teeth; A. wegeneri has five premaxillary (Figure 49B), eleven or twelve maxillary teeth, and an undetermined number of dentary teeth. In general, the teeth of A. tsangatsangana are typical of the heterodont dentition found in most

45 298 A. H. Turner crocodylomorphs. The premaxillary teeth are subcircular in cross-section, slightly recurved and taper to an acute point. The premaxillary teeth increase in size posteriorly with the fourth being the largest and the fifth decreased in size roughly the size of pm3. The first two maxillary teeth are small (roughly the size of the premaxillary teeth) and are followed by a hypertrophied third tooth. These first three teeth are conical, slight recurved, and very weakly compressed mediolaterally. The surface is marked with shallow ridges in the enamel but do not bear any distinct denticles on the carinae, and therefore are not ziphodont (Prasad and Lapparent de Broin 2002). The remaining maxillary teeth decrease in size moving posteriorly and are shorter and more blunt (a spatulate morphology). These teeth are striated and their margins do not bear distinct denticles. The first nine teeth of the dentary are shaped like those of the premaxilla. These teeth increase in size until d5, which is the largest of d1 9, and then decrease in size again. These first nine teeth splay outward and forward slightly, giving a weakly procumbent profile (Figure 41B). The tenth dentary tooth is very unique as it is hypertrophied to the extent of the third maxillary tooth. When occluded, this tooth would rest in a pit between m3 and m4 (1: CorFlip: ). Hypertrophy of dentary teeth is not widespread among basal mesoeucrocodylians. The last tooth in the dental row of Comahuesuchus (MACN P6131) is hypertrophied and there are certain baurusuchids with enlarged dentary teeth (e.g. Baurusuchus pachecoi). In either case, the hypertrophy seen in the other taxa is not similar to that of A. tsangatsangana. It is most similar to that seen in Protosuchus richardsoni (AMNH 3024; Colbert and Mook 1951, Clark 1986). In P. richardsoni, however, the hypertrophied tooth is more anterior in the dental series, resting in a notch between the premaxilla and maxilla. The remaining teeth in the dentary are short and spatulate, decreasing in size posteriorly. Comparison with other Araripesuchus shows a general similarity among the species. The number of premaxillary teeth varies between four and five, but variance in tooth formula is not uncommon (Wermuth 1953). It is uncertain whether the other species of Araripesuchus have a hypertrophied dentary tooth. Only future fossil discoveries or CT imaging of currently known specimens will elucidate this question. Only A. wegeneri deviates substantially from the other species with regards to their known teeth morphology the posterior maxillary teeth of GDF 700 (Figure 7) have distinct denticles on the carinae. Description: Postcranial axial skeleton General form and preservation Much of the cervical region is preserved in FMNH PR 2297 and FMNH PR The atlas is unambiguously represented only by the intercentrum in FMNH PR 2297, which is lying adjacent to what appears to be the atlantal pleurocentrum. These two elements were preserved dislocated from the remainder of the vertebral column, making it unclear as to whether the pleurocentrum was sutured to the axis centrum as the odontoid process. The region between the atlantal elements and the vertebral column was not prepared out, but CT images reveal an area littered with broken fragments of bone. In FMNH PR 2297, the vertebrae are preserved in articulation through c5. Much of the dorsal surface of the axis and c3 are obscured by matrix. The right lateral side of c7 is damaged and c1 c5 are partially hidden by rock. CT imagery illuminates some of the obscured detail. In FMNH PR 2298 the entire vertebral series is preserved, terminating posterior to the pelvic girdle. In this series, however, c2 c5 and c8? are the only cervicals exposed. These cervicals are mostly complete but lack neural spines. Two isolated cervical vertebrae (UA 8728 and FMNH PR 2307) were recovered from the block containing the other Araripesuchus tsangatsangana specimens. In both specimens the cervical ribs were attached to their vertebrae with the exception of the atlas and axis ribs, which were disarticulated in FMNH PR 2297 and not preserved in FMNH PR In both, c7 is damaged and the rib of c8 is not articulated to the vertebra. Because the ribs are articulated, much of the dorsal morphology is obscured and CT images provide little help due to the orientation of the vertebral column with respect to the skull. There are at least 14 dorsal vertebrae in FMNH PR This number is likely to be higher given that a few vertebrae may remain unexposed within the block. All of these lack much of their transverse processes and their neural spines are unexposed. There are six dorsals present in the same block with FMNH PR 2298 belonging to a slightly larger individual (FMNH PR 2299). While not fully exposed, these vertebrae are better preserved, retaining their transverse processes and neural spines, and are likely anterior in the dorsal series. Additionally, nine isolated dorsals were recovered from the larger block containing all the described specimens. These are generally well preserved and fully intact. Most of the dorsal ribs are missing and those preserved are generally disarticulated or incomplete. FMNH PR 2297 preserves one dorsal rib in articulation with d12 and a number of others are preserved in close association with their respective vertebrae in FMNH PR The sacrum is complete. It is preserved in FMNH PR 2298 attached to both right and left ilia. Unfortunately, portions of the dorsal surface of the sacrum are all that is exposed. An isolated, mostly complete, sacrum was also recovered (FMNH PR

46 New Araripesuchus from Madagascar ). The anterior sacral vertebra is damaged and only the right rear sacral rib is preserved. The right ilium is also preserved with this sacrum but remains disarticulated from the rib. Only nine vertebrae identifiable as caudal are preserved in association with FMNH PR The vertebrae are rather small and likely come from somewhere in the middle of the series. Only two unambiguously identified haemal arches are preserved with FMNH PR 2298 and only one of these in articulation with its respective vertebra. In addition to these, three isolated but fully intact and prepared caudal vertebrae were recovered from the large block. No bones clearly identifiable as gastralia are present in any of the blocks. Atlas axis complex The neural arch of the atlas is known only from a handful of crocodylomorph taxa, although the structure is well known in crocodylians. Though not unambiguously present (see 2: HorFlip: and Figure 50) in either FMNH PR 2297 or FMNH PR 2298, the atlantal neural arches are known from A. patagonicus (MUC PV 269). In MUC PV 269, the neural arches are ring shaped for the reception of the occipital condyle (Ortega et al. 2000). Like in Crocodylia and Notosuchus terrestris (Pol 2005), however, they do not contact each other dorsally. The intercentrum of A. tsangatsangana (FMNH PR 2297) is similar to that of Hesperosuchus agilis (Clark et al. 2000), Mahajangasuchus insignis (Buckley and Brochu 1999) and Crocodylus porosus (FMNH 15529) an element broader than long with a shallow concavity separating the long capitular facets. In A. patagonicus (MUC PV 269), the atlantal neurapophyses are poorly exposed or damaged. Only the right postzygapophysis is visible, which curves ventromedially. The postzygapophysis is not dorsoventrally deep as in Notosuchus (Pol 2005), but compressed like Alligator. It lacks the small lateral process seen in the latter taxon. It is unclear whether the odontoid process was fused to the axis pleurocentrum and neural arch, although FMNH PR 2298 (Figure 52) suggests that it was. The odontoid is damaged in FMNH PR 2297 with only the remnants of moderately large capitular facets. The atlantal ribs are slender anteriorly, dorsoventrally compressed, and possess a single head (Figure 51). The right atlantal rib is nearly complete, but only the anterior half of the left rib is exposed. The capitulum of the left rib is fully visible revealing a slightly depressed contact facet. The shaft of the rib constricts behind the capitulum and then progressively expands becoming blade-like. The dorsal and medial margins are smooth, lacking any processes. In contrast to the atlas intercentrum, the centrum of the axis is longer than wide (Figures 51 53). A median ridge extends along the ventral surface of the centrum. This ridge is more pronounced anteriorly and diminishes slightly across the length of the centrum. The axial centrum is constricted medially, and on either side shallow depressions run anteroposteriorly. These depressions do not reach the central edges. FMNH PR 2298 lacks its neural spine rendering it Figure 50. FMNH PR 2297, Araripesuchus tsangatsangana. CT imagery of possible atlas neural arch (yellow). A, Anteroventral view of atlas intercentrum (green) and possible neural arch in a three-dimensional CT reconstruction of the skull with the surrounding matrix digitally removed. B, Coronal section showing the same two structures.

47 300 A. H. Turner Figure 51. FMNH PR 2297, Araripesuchus tsangatsangana. Ventral view of anterior cervical vertebral series. Scale ¼ 1 cm. (Photograph by C. Leonard.) impossible to determine its shape. Most crocodyliforms possess a broad, anteroposteriorly expanded axial neural spine. Notosuchus terrestris (Pol 2005) and perhaps Chimaerasuchus (Wu and Sues 1996b) deviate from this general form with axial spines that are reduced in anteroposterior breadth, shifted posteriorly, and triangular in shape (Pol 2005). At least a portion of the axial neural spine of FMNH PR 2297 is viewable in CT imagery (2: CorFlip: ; SagFlip: ; Figure 53). These images suggest that A. tsangatsangana had a neural spine that was slightly broader anteroposteriorly than the succeeding cervical neural spines, and that the axial spine was developed posteriorly to the terminus of the postzygapophyses. The spine was not as broad as modern crocodylians, lacking the substantial anterior extension (cf. Alligator mississippiensis TMM m-7487) seen in those taxa. The spine, however, is not as anteriorly restricted as the axial spine of Notosuchus terrestris (Pol 2005) (Figures 52 54). The axial parapophyses are small and located on the anteromedial edges of the centrum, just dorsal to the median ventral ridge. The left diapophysis of FMNH PR 2298 and the right diapophysis of FMNH PR 2297 are exposed. The diapophyses are larger than the parapophyses and in cross-section they are nearly ovular in shape. Just posterior to the diapophysis there is a shallow circular fossa. The axial rib is doubleheaded and directly contacts the axis on both the parapophysis and diapophysis. Very little area separates the two structures on the centrum. The prezygapophyses are very small, similar to that of Chimaerasuchus but unlike those of Notosuchus. The prezygapophysis projects anteriorly and is nearly vertically oriented (Figure 52). In this respect, it is again similar to the prezygapophysis of Chimaerasuchus (Wu and Sues 1996b). The postzygapophyses are much longer than the prezygapophyses. They originate from the base of the neural spine and project posteriorly, curving laterally slightly. The articular surface does not face ventrally, but instead slants slightly medioventrally giving the articular surface a partial lateral exposure. Due to poor preservation, it is impossible to determine if a suprapostzygapophyseal lamina (sensu Pol 2005) is present on the axis of A. tsangatsangana. The axial ribs in A. tsangatsangana are doubleheaded elements (Figure 51). The capitula of both ribs are preserved in FMNH PR 2297 but the right rib is best exposed. The capitulum is larger and more ovular than the circular tuberculum. The two heads are spaced closely together and both contact their respective articular surfaces on the axial centrum. The shaft of the rib is uniform in breadth, though bent dorsomedially slightly. The dorsal surface of the rib is strongly concave along its entire length. Postaxial cervical vertebrae The neural arch of the third cervical (c3) is partially damaged in FMNH PR 2297 (2: CorFlip: ; HorFlip: ; Figures 51, 53) but preserves

48 New Araripesuchus from Madagascar 301 Figure 52. FMNH PR 2298, Araripesuchus tsangatsangana. Cervical vertebral morphology. A, Left lateral view, showing neural arches and cervical ribs. B, Ventral view of anterior cervical vertebrae. Scale ¼ 1 cm. (Photographs by C. Leonard.) the neural spine and much of the anterior pedicel and prezygapophyses. FMNH PR 2298, although preserving the neural arch, lacks the neural spine on c3 (Figure 52). The neural spine is broader anteroposteriorly than those of the remaining cervicals. There is a slight anterior curvature to the dorsal portion of the spine that is also not present in the remaining cervicals. The neural spine rests posteriorly over the postzygapophyses, but not to the

49 302 A. H. Turner Figure 54. FMNH PR 2297, Araripesuchus tsangatsangana. CT reconstruction of the skull and vertebral column showing the fifth, sixth, seventh, and eighth cervical vertebrae. Vertebrae c5 and c6 demonstrate the posterior position of the neural spine over the postzygapophysis. Figure 53. FMNH PR 2297, Araripesuchus tsangatsangana. Series of sagittal CT sections through the axis vertebra, showing the shape and position of the neural spine. Sections do not exactly bisect vertebra and spine. The lateral-most section (A) just contacts the neural spine, the middle section (B) reveals the anterior extent of the spine, and the medial-most section (C) shows the posterior development of the spine. extent seen in Mahajangasuchus insignis (UA 8654; Buckley and Brochu 1999) resembling more closely the condition seen in modern crocodylians. In other small-bodied mesoeucrocodylians such as Notosuchus and Chimaerasuchus, the spine is centered over the neural pedicels (Pol 2005, Wu and Sues 1996b). Additionally, the neural spines of these taxa are triangular in lateral view, unlike A. tsangatsangana which has a rectangular profile the trait seen most commonly in other crocodyliforms. All the centra of the eight cervical vertebrae (Figures 51, 52, 56) are amphiplatyan to slightly amphicoelous, the prevalent condition among noneusuchian mesoeucrocodylians. The anterior articular surface is circular, although when viewed ventrally this contact appears linear due to the well-developed parapophyses located at the anteroventral corners. There are no distinct hypapophyseal processes on any of the vertebrae. What is present ventrally is a distinct ridge running anteroposteriorly like that seen on the axis. This ridge increases in size on the posterior cervicals. Parapophyses are ovular in lateral view and become larger as one moves posteriorly through the column. The parapophyses are short on the anterior cervicals and directed ventrally with the articular facets expanded.

50 New Araripesuchus from Madagascar 303 Figure 55. FMNH PR 2297, Araripesuchus tsangatsangana. Detail of cervical neural spines, showing suprazygapophyseal laminae as well as cervical rib morphology. (Photograph by C. Leonard.) Moving posteriorly, the parapophyses originate nearer to the dorsoventral midline of the centrum and are directed more laterally than ventrally. Both ventral and dorsal to the parapophysis, there are deep depressions in the wall of the centrum. These depressions are seen in other crocodyliform taxa such as Mahajangasuchus insignis (UA 8654; Buckley and Brochu 1999: Plate 1) and Notosuchus terrestris (Pol 2005). On c3, the flattened diapophyses project ventrally from the neural arch. The diapophyses remain dorsoventrally flattened in the succeeding vertebrae, maintaining a more or less ventrally directed orientation. It is not until c7 that the diapophyses begin to assume a lateral projection approaching the orientation seen in the trunk. All postaxial diapophyses bear flat facets for articulation with the rib tuberculum. The facets of the prezygapophyses are roughly circular. The prezygapophyseal processes of c3 and c4 are directed anterodorsally. The facets are not strictly horizontal but slanted slightly with the articulation surface partially directed medial. This condition closely resembles that seen in most crocodylians. However, in other non-crocodylian mesoeucrocodylians, such as Notosuchus terrestris (Pol 2005) and Chimaerasuchus (Wu and Sues 1996b) the cervical morphology resembles more closely that seen in the posterior cervicals of crocodylians (Pol 2005). The more posterior cervicals of A. tsangatsangana do not have prezygapophyseal processes that vary significantly from the anterior cervicals, although there is slightly more dorsal curvature (FMNH PR 2297). The postzygapophyses are as large as the prezygapophyses. The postzygapophyses of c3 (FMNH PR 2298) are short but the remaining cervicals have long posterior-projecting postzygapophyses that resemble those of the axis. The dorsal surface of the postzygapophyses bears suprapostzygapophyseal laminae. These laminae are not as pronounced as those seen in Notosuchus terrestris. Presence of such laminae on postzyapophyseal processes appears to be common among small-bodied basal mesoeucrocodylians (Pol 2005). The neural arches of the cervical vertebrae are all very similar. They are roughly equal in proportion to dorsoventral and anteroposterior lengths, therefore differing from Notosuchus terrestris or Chimaerasuchus, which have very tall neural arches. From c4 back, the neural spines are centered over the neural arches. The majority of the spines are moderately tall and narrow, but by c7 the spines begin to broaden in lateral view (Figures 54, 55). The lateral surface of the spines are marked by a low ridge that, based on FMNH PR 2297 and CT data (2: rollspinhead), is continuous with the suprapostzygapophyseal laminae (Figure 55). This morphology is also present in A. gomesii (AMNH 24450) but cannot be determined for A. patagonicus (Ortega et al. 2000). The posterior surface of the neural spines is poorly exposed in both FMNH PR 2297 and FMNH PR 2298, with the neural spine of c6 in FMNH PR 2297 the best exposed. On this surface, the spine bears a small median lamina for the attachment of the interspinous ligament (Fürbringer 1876). The presence and extent of this lamina on the other cervical vertebrae cannot be determined. In modern crocodylians, this lamina decreases in size on the posterior cervicals

51 304 A. H. Turner Figure 56. FMNH PR 2307, Araripesuchus tsangatsangana. Isolated partial anterior cervical vertebra in anterior (A), posterior (B), left lateral (C), and dorsal (D) view. Scale ¼ 1 cm. (Photographs by C. Leonard.) (Mook 1921), while in Notosuchus terrestris these laminae remain prominent posteriorly (Pol 2005). Cervical ribs The morphology of the crocodyliform cervical rib is highly conserved within the group (Mook 1921, Colbert and Mook 1951, Whetstone and Whybrow 1983) and the cervical ribs of A. tsangatsangana reflect that conservation (Figures 51, 52A). All postaxial ribs in the new taxon are double-headed. The tuberculum and capitulum are roughly equal in size and separated by a small gap. The shaft of the rib is characterized by being perpendicular to the tubercular and capitular processes. The shaft consists of an anterior process that tapers to an acute point and a dorsoventrally broad posterior process. On the dorsal surface of the shaft is a shallow U -shaped depression running the entire length of the rib and passing between the tuberculum and capitulum. As in other crocodyliforms, the anterior process of each rib is overlapped by the posterior process of the preceding rib with the anterior process resting in the dorsal U -shaped depression. An interesting feature in A. tsangatsangana is the presence of a thin posterodorsally directed lamina projecting from the dorsal surface of the posterior process of the rib shaft (Figures 52A, 96). In larger specimens the projection becomes more pronounced, as well as slightly elevated from the lateral surface of the rib. This forms a more distinct barb-like structure. A similar feature is present on the cervical ribs of Mahajangasuchus insignis (UA 8654). The right rib of the c8 is preserved and marks the transition between cervical and dorsal vertebrae (Figure 57). This division follows the convention used with modern crocodylians in which the last cervical rib is intermediate in form between the posterior cervical ribs and the anterior dorsal ribs (Mook 1921). In A. tsangatsangana, the rib of c8 demonstrates this intermediacy. The tubercular and capitular processes are closely spaced like cervical ribs but the shaft, like in dorsal ribs, is not perpendicular to them. The shaft of the c8 rib is shorter and less curved than the shafts of anterior dorsal ribs and has a more prominent thin anterior lamina that extends to the midpoint of the rib shaft. Dorsal vertebrae All dorsal centra (Figures 58 63) are amphiplatyan to weakly amphicoelous like the cervical centra. The centra of the anterior dorsal vertebrae are asymmetrical. The anterior articular surface is

52 New Araripesuchus from Madagascar 305 Figure 57. FMNH PR 2297, Araripesuchus tsangatsangana. c8 and d1 ribs. c8 showing transitional nature with well-developed anterior thin lamina. (Photograph by C. Leonard.) broader (in the horizontal plane) than the posterior articular surface with the dorsolateral edges expanding and reflecting posteriorly. It is unclear due to poor preservation or exposure the extent of the asymmetry, but it is present on at least the first four dorsal vertebrae. This unique morphology appears to be related to the continued presence of the parapophyses on the lateral surface of the centra of d1 d3 (FMNH PR 2298; Figure 58). A similar condition appears to be present in the anterior dorsals of Mahajangasuchus insignis (Buckley and Brochu 1999: Fig. 7, plate 1). Parapophyses on d1 d3 may be primitive for crocodyliforms (its unknown in Protosuchus), but is found within crocodylians. In crocodylians, however, the anterior borders of the centra are not expanded as Figure 58. Position of parapophyses on vertebrae d1-d3 in Araripesuchus tsangatsangana. A, Left ventrolateral view of d1 and d2 (FMNH PR 2298), showing parapophyses on neural arch and centrum body. B, Right lateral view of d2 and d3 (FMNH PR 2299). Scale ¼ 1 cm. (Photograph by C. Leonard.)

53 306 A. H. Turner Figure 59. Araripesuchus tsangatsangana. Comparison of isolated vertebrae in anterior view. A, Anterior dorsal vertebra, FMNH PR B, Mid-dorsal vertebra, FMNH PR C, Posterior dorsal vertebra, FMNH PR D, Caudal vertebra, FMNH PR Scale ¼ 1 cm. (Photographs by C. Leonard). in A. tsangatsangana. The lateral surface of the anterior centra bears a shallow depression just ventral to the transverse process. Hypapophyses are presence on the ventral surface of the centra of d1 d3, unfortunately d4 is not sufficiently preserved in either FMNH PR 2297 or FMNH PR 2298 to determine the presence or absence of a hypapophysis. The remaining dorsal centra lack hypapophyses. Distinct parapophyses are present on the centra of d1 d3 on FMNH PR This in unsurprising given that this condition is found in Crocodylia (Mook 1921). Based upon this observation, three isolated vertebrae (FMNH PR 2299; Figure 58B) on the block containing FMNH PR 2298 are interpreted as d1, d2, and d3 of an additional A. tsangatsangana individual. These vertebrae nicely preserve the right lateral surface. The swelling of the anterior surface of the centra in the first few dorsal vertebrae looks to be correlated with the presence of the parapophyses on the dorsal centra. It is unclear how far back the parapophyses are present on the centra due to a lack of preserved dorsal vertebrae between d3 and d6 (FMNH PR 2298). The transverse processes of d1 d3 (FMNH PR 2298; Figure 58) are nearly cylindrical. The distal surfaces bear circular diapophyseal contact surfaces. By d6, the tubercular and capitular contact facets are both located on the transverse process. These processes are initially narrow but become longer and anteroposteriorly broad by the mid-dorsals. The transverse processes of the posterior dorsals narrow slightly. The distal-most end of these processes (in FMNH PR 2298) is damaged, so their morphology remains uncertain. In the isolated dorsals, the vertebrae with long, broad transverse processes are rugose at their ends. The rugosity may be from ligamentous attachment of the ribs. In crocodylians, the transverse processes of the posterior-most dorsals are situated with their distal ends directed slightly to the anterior. In Notosuchus terrestris, this condition is not present the transverse processes are perpendicular to the long

54 New Araripesuchus from Madagascar 307 Figure 60. Araripesuchus tsangatsangana. Comparison of isolated vertebrae in posterior view. A, Anterior dorsal vertebra, FMNH PR B, Mid-dorsal vertebra, FMNH PR C, Posterior dorsal vertebra, FMNH PR D, Caudal vertebra, FMNH PR Scale ¼ 1 cm. (Photographs by C. Leonard.) axis of the vertebrae (Pol 2005). The posterior dorsals of A. tsangatsangana are poorly preserved in FMNH PR 2298, but isolated vertebrae interpreted as posterior dorsals and the posterior dorsals of A. gomesii (AMNH 24450) suggest that these two species of Araripesuchus closely resemble Notosuchus terrestris in this respect. Anteriorly, the dorsal vertebrae have prezygapophyses with oval dorsomedially-facing facets. The zygapophyses just barely project past the anterior margin of the centra. The prezygapophyseal processes are robust throughout the trunk and bear a lateral ridge running to meet the transverse process and a distinct dorsal ridge extending onto the lower surface of the neural spine. Moving posteriorly, the prezygapophyseal facets enlarge and face dorsally. The processes become shorter and more robust, and the prezygapophysis as a whole lies closer to the transverse process, failing to extend past the anterior margin of the centra. The dorsal ridge becomes broader and now describes the posterior wall of the depression in which the postzygapophysis of the preceding vertebra rests. The prezygapophyses of the posterior dorsals in A. tsangatsangana do not extend out laterally to the extent seen in modern crocodylians. The postzygapophyses of the anterior dorsals are small with ventrolaterally-facing facets. These zygapophyses extend just past the posterior margin of the centra. Moving posterior, the postzygapophyses enlarge and expand well beyond the posterior border of the centra, but do not extend laterally to the extent seen in crocodylians. Although, the oblique orientation of the postzygapophyseal facets diminishes posteriorly, they never become truly horizontal. In this respect, A. tsangatsangana is similar to most neosuchians and unlike Notosuchus terrestris (Pol 2005), Chimaerasuchus paradoxus (Wu and Sues 1996b; IVPP V8274), and Uruguaysuchus aznarezi (Rusconi 1933) (Figure 60). Again, differing from the basal mesoeucrocodylians mentioned above, the postzygapophyses of A. tsangatsangana are positioned higher than the transverse processes. This is the condition found in extant taxa

55 308 A. H. Turner Figure 61. Araripesuchus tsangatsangana. Comparison of isolated vertebrae in dorsal view. A, Anterior dorsal vertebra, FMNH PR B, Mid-dorsal vertebra, FMNH PR C, Posterior dorsal vertebra, FMNH PR D, Caudal vertebra, FMNH PR Scale ¼ 1 cm. (Photographs by C. Leonard.) (Mook 1921) and in early crocodylomorphs such as Dibothrosuchus (Wu and Chatterjee 1993). In taxa such as Notosuchus terrestris and Chimaerasuchus paradoxus, the postzygapophyses are level with the transverse processes. Suprapostzygapophyseal laminae are present but greatly reduced in the dorsal vertebrae, although the laminae appear slightly more prominent posteriorly. This may, however, simply be due to the generally larger size of the posterior dorsals. In posterior view, the two postzygapophyses form a medial triangular sulcus between them. This sulcus is very shallow in the anterior dorsals but deepens toward the sacrum, and the postzygapophyses enlarge. In modern crocodylians (e.g. Alligator sinensis) a similar structure is present but its morphology is significantly different from that seen in Araripesuchus tsangatsangana. In Araripesuchus tsangatsangana, the lateral walls of the sulcus are formed from the postzygapophyses and the suprapostzygapophyseal laminae as they extend dorsally to contact the neural spine. The posterior medial thin lamina descends down the midline of the sulcus to contact the median small triangular fossa. The only exposure of the neural spine in the sulcus is from the medial thin lamina and the dorsal edges of the triangular foramen (Figure 61). In Alligator sinensis, the sulcus-like structure is not very deep. The lateral walls of the structure are formed, like in Araripesuchus, by the postzygapophyses. In Alligator, however, the dorsal edge of the sulcus is poorly defined because no suprapostzygapophyseal laminae are present. The posterior medial thin lamina is not well developed in Alligator and is often reduced or absent in crocodylians (Mook 1921). Therefore, the sulcus is not bisected by the lamina as it is in A. tsangatsangana. Instead, what occurs is the extension of the lateral laminae of the neural spine past the posteromedial limit of the postzygapophyses. Indeed, what happens is a literal division, by the neural spine, of the sulcus in two. With full extension of the neural spine between the postzygapophyses what was a small triangular foramen in Araripesuchus tsangatsangana (Figure 60) becomes in Alligator a large V -shaped groove on the posterior of the vertebra. The neural spines of the dorsal vertebrae are about as tall as those seen in extant taxa. The spines broaden anteroposteriorly as one moves toward the sacrum. The dorsal terminus of the spine does not flare like in crocodylians, but remains relatively similar in thickness compared to the rest of the spine. Anterior and posterior thin laminae are present on the spine and become more pronounced in the posterior dorsals.

56 New Araripesuchus from Madagascar 309 Figure 62. Araripesuchus tsangatsangana. Comparison of isolated vertebrae in left lateral view. A, Anterior dorsal vertebra, FMNH PR B, Mid-dorsal vertebra, FMNH PR C, Posterior dorsal vertebra, FMNH PR D, Caudal vertebra, FMNH PR Scale ¼ 1 cm. (Photographs by C. Leonard.) A small depression is present on the lateral surface of the neural spine between the prezygapophysis and the postzygapophysis in the anterior dorsals. This depression disappears posteriorly. Dorsal ribs Few dorsal ribs are preserved and/or identifiable from A. tsangatsangana. The ribs of d1 d4 are preserved in FMNH PR These first four ribs have both capitular and tubercular processes, with the former being the longer of the two. The shafts of these first three ribs bear distinct anterior flanges. It is unclear whether the rib of d4 possessed a similar flange. Little can be said generalizing the change in rib morphology throughout the trunk due to the paucity of rib remains. When present and preserved, the capitular and tubercular facets are circular and subequal in size. The capitulum typically lies on a longer process than the tuberculum. Separating these two processes is a shallow, ventrally-directed triangular depression that is interpreted as the costal groove. In the more posterior dorsals, a distinct tuberculum is not present. The shafts of the dorsal ribs are all gently curved and roughly circular in cross-section. The ribs are broad near the head and taper to a flattened end that is slightly larger than the preceding portion of the shaft. This distal swelling of the rib shaft is not as pronounced in Araripesuchus as it is in modern crocodylians. The anterior surface of the dorsal ribs, posterior to d4, are not smooth but bear a short broad anterior-directed flange. This most likely provided a larger attachment surface for intercostal muscles. Present in both A. tsangatsangana (FMNH PR 2298) and A. gomesii (AMNH 24450) are small conical,

57 310 A. H. Turner Figure 63. Araripesuchus tsangatsangana. Comparison of isolated vertebrae in right lateral view. A, Anterior dorsal vertebra, FMNH PR B, Mid-dorsal vertebra, FMNH PR C, Posterior dorsal vertebra, FMNH PR D, Caudal vertebra, FMNH PR Scale ¼ 1 cm. (Photographs by C. Leonard.) acutely tipped spikes associated with the anterior dorsal vertebrae. These spikes are likely homologous to the cartilaginous uncinate processes present in living crocodylians. Supporting this interpretation is the fact that the spikes of Araripesuchus are located on (or found in association with) the posterodorsal surface of the rib shaft, which is where the uncinate processes of crocodylians originate (Hoffstetter and Gasc 1973). Additionally, in some species of Alligator the uncinate processes are known to ossify slightly (Mook 1921). Sacrum As with other Araripesuchus sacra, the sacrum of A. tsangatsangana (UA 8767, FMNH PR 2301; Figure 64) consists of two sacral vertebrae the conserved condition of most crocodylomorphs. The rare exception to this has been noted in Notosuchus terrestris, which possesses three fused sacral vertebrae (Pol 2005; however, see discussion therein). The sacral vertebrae of FMNH PR 2301 are largely fused to each other, both at their centra and at their zygapophyses, though the neural spines of the two vertebrae remain unfused and distinct. The right side of the first sacral is mostly missing. The centrum of this vertebra is roughly the size and shape of the posterior dorsals, however, the anterior articular surface of the centrum is greatly expanded in the horizontal plane and forms a deeply concave surface. This concavity is formed largely by the anterolateral expansion of the flanking parapophyses of the centrum. The posterior contact surface of the centrum is straight and fused with the second sacral vertebra.

58 New Araripesuchus from Madagascar 311 Figure 64. FMNH PR 2301, Araripesuchus tsangatsangana. Partial sacrum in anterior (A), posterior (B), left lateral (C), right lateral (D) and ventral (E) view. Scale ¼ 1 cm. (Photographs by C. Leonard.) The ventral surface of both sacrals is marked by a shallow anteroposteriorly oriented groove. The centrum of the second sacral vertebra is much wider than that of the first, though the length of the two vertebrae is similar. The anterior surface is flat and the posterior surface bears a deep cotyle. The cotyle is unlike that of modern crocodylians (Mook 1921). It is very broad and dorsoventrally narrow, being formed, in part, by the enlarged and posteriorly shifted parapophyses. Together, the parapophyses form nearly two-thirds of the surface area of the cotyle. The sacrum of A. tsangatsangana is interesting, with the deeply concave anterior surface of the first sacral vertebra and the deep cotyle on the posterior of the second. It is unclear whether the centrum of the preceding vertebra (in the case of the first sacral) and the succeeding vertebra (in the case of the second sacral) had a developed condyle for articulation with these vertebrae. If the presence of a condyle were in fact the case, then the anterior articulation would be, in a way, pseudo-procoelous and the posterior pseudoopisthocoelous. The prezygapophyses of the first sacral are not preserved. The postzygapophyses of the first are fused to the prezygapophyses of the second sacral, though not reduced in size like Notosuchus terrestris (Pol 2005).

59 312 A. H. Turner In size and location on the neural arch, the pre- and postzygapophyses are similar to those of the posterior dorsals. The sacrum is connected to the ilia via expanded sacral ribs. Only the posterior right transverse process is preserved in FMNH PR Like most crocodyliforms, this process and its attached rib is broad with a long posterior extension resulting in a substantial contact surface with much of the medial area of the ilium. The second sacral rib is firmly fused to the transverse process and the greatly enlarged posteriorly-shifted parapophysis. Both sacral vertebrae lack neural spines (Figure 64). Caudal vertebrae Nine caudal vertebrae are preserved in FMNH PR 2298 (Figure 65). In addition to this, five isolated caudals were found and fully prepared (Figures 59D 63D, 65). The total number of caudal vertebrae for any Araripesuchus species is not known. A. gomesii (AMNH 24450) is the most complete specimen known and it preserves 21 caudal vertebrae (Hecht 1991). This number reflects a nearly complete tail, with only the distal-most portion missing. Only three chevrons are preserved with FMNH PR 2298, two of which are associated with their respective vertebrae. All caudal centra are amphiplatyan to weakly amphicoelous. Without definitive anterior caudal vertebrae identified, it remains unclear the shape of the anterior caudal centra. In A. gomesii (AMNH 24450), the first two caudal centra are broad like the posterior dorsal centra. Posterior to the second caudal, the centra become more slender. All preserved caudal centra of FMNH PR 2298 are rather long and slender and constricted at their midpoint. Running anteroposteriorly along the entire length of the ventral surface are two ridges, which appear as continuations of the lateral walls of the centrum. A deep depression separates Figure 66. FMNH PR 2299, Araripesuchus tsangatsangana. Haemal arch in lateral view. Scale ¼ 1cm. (Photograph by C. Leonard.) the ridges. This morphology is similar to that seen in modern crocodylians (e.g. Alligator sinensis). The caudals bear tall neural spines. The spines are not as broad as the spines of the dorsal vertebrae. Posterior thin laminae are absent, though in some caudals distinct anterior thin laminae are present. The progression of neural spine height is not known for A. tsangatsangana because most are obscured in FMNH PR The transverse processes are narrow and slant to the posterior slightly. The anterior edge of the process contacts the posterior edge of the prezygapophysis, similar to what is seen in Notosuchus terrestris (Pol 2005). In the anterior-most five caudals, the transverse processes are long, but the length gradually diminishes in the succeeding caudals. The prezygapophyses are similar on the anterior caudals to those of the presacral column roughly circular facets facing dorsomedially. The postzygapophyses are similarly like those of the presacral vertebrae. The postzygapophyses are located dorsal to the level of the transverse process and lack suprapostzygapophyseal laminae. Of the three chevrons present in FMNH PR 2298 two are in roughly articulated position with their vertebrae (Figure 66). This, in conjunction with the anteroventrally directed articulation facets on the ventral surface of the caudal centra, demonstrates that the chevrons are intersegmental. The chevrons are characteristically V -shaped in anterior view. Figure 65. FMNH PR 2308, Araripesuchus tsangatsangana. Isolated caudal vertebra in ventral view. Scale ¼ 1cm. (Photograph by C. Leonard.) Description: Appendicular skeleton Shoulder girdle general form and preservation No articulated shoulder girdle is preserved intact in any of the slabs. FMNH PR 2297 preserves a partial left and right scapula and nearly complete right coracoid. The left scapula is only a portion of the scapular blade, but the right is nearly complete. FMNH PR 2334 has a nearly complete left scapula with only the anterior-most margin damaged. Also recovered was an isolated left scapula and coracoid

60 New Araripesuchus from Madagascar 313 Figure 67. FMNH PR 2313, Araripesuchus tsangatsangana. Articulated left scapula and coracoid in lateral (A) and posterior (B) view. Scale ¼ 1 cm. (Photographs by C. Leonard.) (Figure 67). These are in good condition, only lacking material from the anterior edge of the scapula. The scapula is remarkable in its proportionally broad scapular blade compared to the length of the scapulocoracoid articulation. The scapular blade is generally about as broad as the scapulocoracoid articulation in most other crocodyliforms, although the blade can be broader in general in some basal mesoeucrocodylians (e.g. Notosuchus terrestris, Chimaerasuchus paradoxus) than in crocodylians. The glenoid fossa opens posteriorly and is predominately comprised of the coracoid, with roughly one-third of the fossa formed by the scapula. The glenoid surface is smooth. No scapula or coracoid is preserved in full articulation, but specimen FMNH PR 2313 consists of a scapula and coracoid that articulate with one another. The dorsal surface of the coracoid and ventral surface of the scapula are relatively smooth, lacking any sign of interdigiting between the two elements. Therefore, it appears likely that the synchondrosis between the two elements was open in all preserved A. tsangatsangana individuals. Distinction between scapula and coracoid is the pervasive condition among crocodylians (Reese 1915, Mook 1921) and is seen in early crocodylomorphs as well (Wu and Chatterjee 1993, Clark et al. 2000). An open synchondrosis at most indicates that these individuals were not greatly advanced past maturity (Brochu 1995), that is, if the primitive condition for Crocodylia holds true for other mesoeucrocodylians. Scapula The scapula is characteristically crocodylomorph, with a constricted area separating a broad dorsal blade from a ventral expansion that bears the dorsal wall of the glenoid fossa (Figure 68). Apart from this, the scapula differs significantly from the shape seen in living crocodylians, which have relatively narrow scapular blades compared to the ventral margin. In A. tsangatsangana, the blade of the scapula is

61 314 A. H. Turner Figure 68. FMNH PR 2313, Araripesuchus tsangatsangana. Left scapula in lateral (A) and medial (B) view, showing muscle scarring. Scale ¼ 1 cm. (Photographs by C. Leonard.) extremely broad. The dorsal edge is high and convex, sloping steeply anteriorly to form a strongly concave anterior margin. The shape of the scapula is very similar to that of Mahajangasuchus insignis (UA 8654). Buckley and Brochu (1999) regarded a scapular blade twice as wide as the scapulocoracoid articulation diagnostic for an unnamed clade containing Mahajangasuchus, Araripesuchus, Peirosauridae and Trematochampsa. Other mesoeucrocodylians have broad scapulae (e.g.

62 New Araripesuchus from Madagascar 315 Notosuchus terrestris, Malawisuchus mwakayasyunguti, Chimaerasuchus paradoxus and Uruguaysuchus aznarezi) as well as some basal alligatoroid crocodylians (e.g. Wannaganosuchus and Diplocynodon), however, in these taxa the expansion of the scapular blade is not as extensive as in Araripesuchus and Mahajangasuchus. The posterior margin of the scapula is slightly rugose from the attachment of the M. serratus superficialis. Ventral to this and near the constriction in the scapula, there is small ovular scar, distinct from the superficial serratus muscle scar, which is likely the attachment point for the M. scapulohumeralis posterior (Fürbringer 1876). The anterior-most margin of the scapula is missing in all specimens rendering identification of muscle scarring problematic. The lateral margin of the scapular blade is noteworthy for its prominent longitudinal ridge, subdividing the surface. Living crocodylians posses this ridge, which is very subtle as it is simply a demarcation between the shallow sulci formed from the attachment of M. teres major and M. dorsalis scapulae (Fürbringer 1876). Contrasting this is the condition in A. tsangatsangana. In this taxon, the ridge is very distinct (sr1) and nearly continuous with a smaller ridge above the glenoid (sr2). The anterior sulcus is very deep and forms a partial second longitudinal ridge. This deep sulcus may imply an enlargement of the M. dorsalis scapulae. The posterior sulcus is shallow but broad. A very low and indistinct ridge (sr3) subdivides the surface of the posterior sulcus. A similarly distinct ridge is present in A. patagonicus (Ortega et al. 2000) and to a lesser extent in A. gomesii (AMNH 24450). Again, Araripesuchus shares similarity in scapular morphology with Mahajangasuchus, which indeed has a relatively prominent longitudinal ridge (Buckley and Brochu 1999; Plate 2). An enlargement of this ridge appears not to be directly correlated with an expansion of the scapular blade. Other crocodyliforms that have scapulae broader than other crocodylomorphs do not posses a more distinct than average ridge. Notosuchus terrestris has a very subtle ridge (pers. obs.) but Pol (2005) did not figure its presence. Wu and Sues (1996b) also figured Chimaerasuchus paradoxus with a laterally smooth scapular blade. Ventrally, the scapula expands into a rectangular base contacting the coracoid and forming the dorsal one-third of the glenoid. It is unclear whether an acromial crest is present anteriorly, although its presence in A. patagonicus and A. gomesii makes its presence likely. Dorsal to the glenoid, there is a distinct crest similar to what is seen in Mahajangasuchus insignis (UA 8654) but continuing farther dorsally (Figure 68A). In Notosuchus terrestris, a crest dorsal to the glenoid (Pol 2005) is present but it is not as pronounced as in A. tsangatsangana. Living crocodylians lack this ridge, although a ridge-like rugose tubercle is presence above the glenoid (pers. obs.) This rugosity is associated with the attachment of M. triceps scapularis (Fauvel 1879, Brochu 2003). In A. tsangatsangana (as well as Mahajangasuchus insignis and Notosuchus terrestris), this rugosity is present on the ridge dorsal to the glenoid. Additionally, in A. tsangatsangana the rugosity faces posterior, contrasting the condition in crocodylians in which the rugosity faces laterally (Brochu 1992). This posterior shift in the attachment of the M. triceps scapularis likely reflects the more posteriorly oriented glenoid of Araripesuchus. The medial surface is marked by a deep depression corresponding to the M. subscapularis. On the ventral-most point, along the straight posterior edge, there is a very small swelling. This seems likely to correspond to the attachment point for the M. ancones coracoscapularis (Fürbringer 1876). Coracoid The coracoid is gracile, comprised of an enlarged dorsal glenoid region followed ventrally by a narrow tubular shaft that expands distally (Figure 69). The wide dorsal region contacts the scapula in a more or less straight line. This area is perforated by a small coracoid foramen, similar to the condition in Chimaerasuchus paradoxus (Wu and Sues 1996b), Uruguaysuchus aznarezi (Rusconi 1933), and Notosuchus terrestris (Pol 2005). Also like these taxa, the foramen in A. gomesii (AMNH 24450), A. patagonicus (MUC PV 269), and A. tsangatsangana (FMNH PR 2313) is situated very close to the glenoid region. The coracoid comprises the ventral two-thirds of the glenoid fossa. The surface of the glenoid facet is greatly expanded, slightly concave, and faces posteriorly. There is a small swelling along the dorsal contact with the scapula, while the ventral portion is pendulous and completely separated from the shaft of the coracoid. This area under the glenoid is marked by a very deep recess, which is bordered medially by a thin lamina extending from the medial edge of the glenoid fossa down the proximal half of the coracoid shaft. An enlarged posterior-facing glenoid facet was noted in Chimaerasuchus paradoxus (Wu and Sues 1996b), as well as Notosuchus terrestris (Pol 2005) and Uruguaysuchus aznarezi (Rusconi 1933: fig. 16). None of these taxa, however, have the deep recess ventral to the glenoid that A. tsangatsangana (Figure 69C) or A. gomesii has. The coracoid of A. tsangatsangana is interesting, differing from the typical crocodyliform in a number of ways. The coracoid is very long. Indeed, the length of the coracoid is slightly greater than that of the scapula. Clark (1994) considered a subequal scapula and coracoid a synapomorphy for all neosuchians with the exclusion of atoposaurs. If dyrosaurids and

63 316 A. H. Turner Figure 69. FMNH PR 2313, Araripesuchus tsangatsangana. Left coracoid in lateral (A), medial (B), and posterior (C) view, showing muscle scarring. Scale ¼ 1 cm. (Photographs by C. Leonard.) Pholidosaurus are removed from analysis (see Clark 1994; Brochu et al for discussion of this) than this character is optimized as a non-hsisosuchus mesoeucrocodylian synapomorphy (Buckley and Brochu 1999, Brochu et al. 2002). The presence of the trait within Araripesuchus suggests that even under an unconstrained scenario the feature occurs earlier in Mesoeucrocodylia than Neosuchia. The shaft of the coracoid is also distinct as it is narrow and nearly tubular for much of its length. Chimaerasuchus paradoxus and Uruguaysuchus aznarezi approach this morphology, but in both taxa the shaft begins to broaden earlier and more gradually than A. tsangatsangana. The ventral end of the coracoid is distally expanded, as is the case in most crocodyliforms. Unlike most crocodyliforms, however, this expansion is asymmetrical the anterior edge is strongly expanded and curves anteriorly. Again, it appears this morphology is present in Chimaerasuchus paradoxus and Uruguaysuchus aznarezi, however, in both taxa the distal end of the coracoid is damaged so determination remains equivocal. Interestingly, the coracoid of A. gomesii differs from A. tsangatsangana in the features discussed above. Although long, the coracoid of A. gomesii does not have the narrow tubular shaft. The glenoid facet is enlarged and pronounced ventrally like in A. tsangatsangana, however, it lacks the deep recess under the facet. Most interesting is the expansion of the distal end. In A. gomesii, the expansion begins earlier and more gradually than A. tsangatsangana. Moreover, the expansion is not asymmetrical, with the posterior edge strongly pronounced and projecting posteriorly. Whether further variation within Araripesuchus exists is uncertain, as no coracoid is preserved in A. patagonicus. Several specific muscle scars are visible on two of the coracoids, FMNH PR 2313 and UA Most prominent is the moderately large tubercle located roughly halfway down the posterior margin of the shaft. This likely corresponds to the attachment surface for the M. triceps brachii seen in crocodylians (Fürbringer 1876, Fauvel 1879). In crocodylians, two of the three heads of the M. triceps brachii attach to the coracoid (Fauvel 1879). The tubercle described above appears to correspond to the long head of the triceps brachii. The prominent lamina dorsal to this tubercle and located under the glenoid may reflect an enlargement of the attachment surface for the caput coracoideum of the triceps. This is unclear, but the lamina roughly corresponds topologically with the origin of this head of the triceps in Alligator (Fauvel 1879). Also along the posterior rim, but ventral to the triceps tubercle, is a shallow sulcus extending down the remainder of the coracoid margin. This likely received the costicoracoideus muscle. In lateral view, weak striations define the outline of the coracobrachialis attachment area. Unlike modern crocodylians, which have a large anterolaterally located rugose tubercle formed from the attachment of the large biceps brachii muscle (Fürbringer 1876, Brochu 1992), A. tsangatsangana lacks a tubercle and

64 New Araripesuchus from Madagascar 317 no region for biceps attachment is apparent on either FMNH PR 2313 or UA Forelimb general form and preservation No complete forelimb was preserved in any of the slabs. Three left and four right humeri were recovered (UA 8721, FMNH PR 2297, FMNH PR 2298, FMNH PR 2302, FMNH PR ). The humeri are typically well preserved and predominantly intact (Appendix E). Epipodial and podial elements are scarcer. Two partial forelimbs (FMNH PR 2324, FMNH PR 2326) were recovered. FMNH PR 2324 consists of a left humerus with its distal end obscured, a partial radius (the proximal end) and a near complete ulna with the posterior surface exposed. This forelimb may pertain to an isolated right humerus (FMNH PR 2327) located nearby on the slab. The second forelimb, FMNH PR 2324, consists of an ulna, distal portion of a radius, radiale, ulnare, and pisiform carpal as well as various phalanges that may be associated with the manus. Recovered isolated from this slab was the proximal two-thirds of a right ulna, the distal half of a radius, two right radialia, as well as a right radiale and ulnare with the distal half of a metacarpal. Additional podial elements were preserved associated with one another on slab three (FMNH PR 2328). These are interpreted as MC II, III, IV, and the three phalanges of digit II. Humerus The humeri of A. tsangatsangana, as well as other Araripesuchus taxa, are very gracile compared to modern crocodylians. Humeral gracility can be difficult to determine as larger animals will have larger bones and tend to appear more robust as a reflection of their size. However, the degree of robustness or gracility is size independent, and is here taken to be reflected in the ratio between midshaft width and the long-axis length of a particular element in this case the humerus. Another point of ambiguity is exactly where to draw the line between what is considered gracile and what is considered robust. Since the ratio discussed above ranges continuously between 0 and 1, a line draw between gracile and robust is most likely arbitrary, although this arbitrary distinction may diminish within the context of specific clades. As a result, the gracility of certain skeletal elements may be of little phylogenetic importance, while retaining descriptive importance. Gracility of the humerus varies among crocodylomorph taxa. As a convention, I am considering a humerus to be gracile if its ratio between midshaft length and long-axis length is less the 0.10 and robust if the value is 0.10 or higher. This value of 0.10 was selected because taxa typically viewed as gracile (e.g. Terrestrisuchus gracilis) fall below this value, while taxa typically viewed as robust (e.g. Crocodylus robustus) fall above this value. Early crocodylomorphs such as Sphenosuchus (Walker 1990), Dibothrosuchus (Wu and Chatterjee 1993), and Terrestrisuchus (Crush 1984) have gracile humeri. Crocodylians like Alligator (FMNH ) and Crocodylus (Mook 1921) have robust humeri with ratios well above Pol (2005) noted that some basal mesoeucrocodylians such as Notosuchus terrestris, Uruguaysuchus aznarezi and Chimaerasuchus paradoxus have robust humeri similar to that seen in Crocodylus. Malawisuchus mwakayasyunguti, a crocodyliform typically regarded as closely related to Notosuchus terrestris (Wu and Sues 1996b, Gomani 1997, Pol 1999), however, has gracile humeri more similar to the dimensions seen in Terrestrisuchus and Araripesuchus. The humerus of A. tsangatsangana is expanded at both ends and bears a prominent deltopectoral crest (Figure 70). The shaft is straight, narrow, and nearly cylindrical. The humerus lacks the lateral bend midshaft like modern crocodylians exhibit. A similarly straight humerus was noted in A. patagonicus (Ortega et al. 2000) as well as in A. gomesii (AMNH pers. obs.; Hecht 1991). The deltopectoral crest is thin, generally smooth, and located on the lateral margin of the humerus, extending distally roughly one-third of the length of the humerus. There are tuberosities found dorsal to the crest near the proximal humeral head and on the anterior apex of the crest. In lateral view, the crest is triangular in shape with a convex lateral profile and a concave anterior profile. The relative size and position of the crest is similar to Terrestrisuchus gracilis (Crush 1984), Uruguaysuchus aznarezi (Rusconi 1933: fig. 12) and Mahajangasuchus insignis (Buckley and Brochu 1999), but is unlike the strongly medially shifted crest of Notosuchus terrestris (Pol 2005; pers. obs.). The proximal head is wider than the distal articular surface. The humeral head slants slightly posteriorly and bears an ovular depression just below the proximalmost end on both the posterior and anterior surfaces. Similar depressions are found on the posterior surface of the humeral head in Notosuchus terrestris (Pol 2005), Chimaerasuchus paradoxus (Wu and Sues 1996b), Uruguaysuchus aznarezi (Rusconi 1933: fig. 12), and Mahajangasuchus insignis (Buckley and Brochu 1999). The distal end is damaged in most preserved humeri but is well preserved in UA 8721 and FMNH PR 2302, revealing several interesting features. As in Notosuchus terrestris (Pol 2005), Uruguaysuchus aznarezi (Rusconi 1933: fig. 11) and other Araripesuchus species (A. gomesii AMNH 24450; A. patagonicus Ortega et al. 2000), two supracondylar ridges run proximo-distally near the distal end of the humerus on both the anterior and posterior surfaces. These ridges enclose, and partially form, small depressions with the posterior depression larger and longer than the anterior one. As noted by Pol (2005) on Notosuchus,

65 318 A. H. Turner Figure 70. FMNH PR 2302, Araripesuchus tsangatsangana. Left humerus in proximal (A), distal (B), lateral (C), posterior (D), medial (E), and anterior (F) views. Scale ¼ 1 cm. (Photographs by C. Leonard.) the medial ridge in A. tsangatsangana is more prominent on the anterior surface, while the lateral ridge is more prominent on the posterior surface. The lateral surfaces of the distal part of the humerus are broad and flat, as in Uruguaysuchus aznarezi (Rusconi 1933: fig. 11) and other Araripesuchus species (AMNH 24450; Ortega et al. 2000). The two articular condyles are not equally developed. The capitellum is larger and broader anteriorly than the medial convexity. Although smaller, the medial convexity extends farther distally, creating a slight anterolateral to medial slant to the articular surface. The two condyles are separated by a moderately deep trochlea, which is continuous with the depression formed by the supracondylar ridges on the anterior and posterior surfaces of the humerus. In living crocodylians, the articular surfaces predominantly face anteriorly, or in life position, ventrally the humerus is held parallel to the ground. In A. tsangatsangana, the articular surface does not face anteriorly but is deflected ventrally at roughly a 458 angle. This is not as severe a condition as in the basal crocodylomorph Terrestrisuchus gracilis (Crush 1984), whose humeral articular condyles face directly ventral, but is more pronounced than living crocodylians. Therefore, suggesting a more upright forelimb posture for A. tsangatsangana. Ancestrally in crocodylians, the insertion of M. teres major is indicated by a tubercle on the posterior (dorsal in life position) surface of the humeral head near the angle delimiting the posterior surface of the head from the deltopectoral crest (Brochu 1992, Meers 2003). Muscle scarring on the humeral head of A. tsangatsangana differs from the condition seen in crocodylians in a number of aspects. No tubercle is present posteriorly, but a rugose depression is located on the deltopectoral crest near the back of the humeral head. Bordering this rugosity, proximally, is an elongate rugosity interpreted here as the proximal insertion of M. deltoideus scapularis (Brochu 1992, Meers 2003). Opposite this insertion and projecting distally from the ventral border of the rugose depression is a low ridge extending along the diaphysis, curving gently anteriorly along its path. The ridge terminates just past the midpoint of the humerus. This ridge is likely the muscle scar associated with the area between the lateral and medial heads of the triceps brachii (Fauvel 1879, Meers 2003). Given the close topographical correspondence with the triceps, deltoid, and humeroradialis muscles, the rugose depression on the deltopectoral crest is identified here as the muscle scar for the M. teres major. All Araripesuchus taxa with described humeri bear the attachment scar for the teres major on the posterior border of the deltopectoral crest (Figure 71). The right

66 New Araripesuchus from Madagascar 319 Figure 71. Detail of humeral muscle scarring. A, Posterolateral view of left humeral head (FMNH PR 2325). B, Medial view of distal condyle of right humerus (UA 8721). C, Lateral view of distal condyle of right humerus (UA 8721). Scale ¼ 1 cm. (Photographs by C. Leonard.) humerus of Uruguaysuchus aznarezi appears to posses a similar muscle scar on the deltopectoral crest and Rusconi figured an ovular depression on the left humerus (Rusconi 1933: fig. 12). Additionally, Wu and Chatterjee (1993) noted a depression in a similar location in Dibothrosuchus. The posterior surface of the humeral head, just distal to the proximal condyle, bears a deep concavity (Figure 71A), which corresponds to the insertion of M. scapularis humeralis caudalis (Meers 2003). This attachment surface is located more proximally in A. tsangatsangana than in extant crocodylians. Distally, on the anterior surface near the condyles, there is an enlarged region for the attachment of M. brachioradialis (Fürbringer 1876). The medial edge of the condylar surface bears a distinct ridge corresponding to the flexor muscles of the arm (Fauvel 1879, Brochu 1992, Meers 2003; Figure 71C). There is a deep groove passing through this surface proximodistally. It is ambiguous, but the groove may have transmitted a branch of the ulnar nerve. This groove may also represent a distinction between the heads of the pronator teres and the flexor digitorum longus muscles. Ulna Six ulnae (three left and three right) belonging to A. tsangatsangana were recovered (UA 8758, FMNH PR 2298, FMNH PR 2324, FMNH PR , FMNH PR 2339). UA 8758, a right ulna, preserves the proximal two-thirds of the bone (Figure 72). The ulna has a smooth trochlear surface, a portion of which is deflected anteroventrally as in A. gomesii. The proximal end is slightly damaged, but FMNH PR2339 and UA 8758 preserve the posterior portion of the proximal end. A. gomesii (AMNH 24450) preserves what looks like the rudiments of an olecranon, but the presence of this structure in A. tsangatsangana is ambiguous a slight elevation of the area over the surrounding articular surface appears present. Other crocodyliforms, such as Notosuchus terrestris (Pol 2005) and Chimaerasuchus paradoxus (Wu and Sues 1996b), lack an olecranon. Some phylogenetic analyses (Buckley and Brochu 1999, Buckley et al. 2000) place Araripesuchus closer to Mahajangasuchus insignis (which possesses an olecranon) than to Notosuchus and Chimaerasuchus, suggesting that Araripesuchus may possess an olecranon based on inference from phylogeny. Moreover, mature modern crocodylians possess a cartilaginous olecranon (Brochu 2003), which would not necessarily be preserved in the rock record. Overall, the ulna is mediolaterally narrow, although some of this narrowness proximally is due to compression during preservation. The shaft of the ulna is narrow and flares dorsally toward the proximal articular region. The posterior surface just ventral to the olecranon region (UA 8758, FMNH PR 2326) is striated, marking the origination of M. humeroulnophalangei (Brochu 2003; pronator quadratus of Meers 2003). The lateral edge of the anterior part of the trochlear region is rough and striated providing an attachment surface for the supinator muscle. The remainder of the shaft is narrow and lacks the prominent bowing found in many other crocodyliforms. The surface of the shaft is smooth making delineation of muscle scars difficult. A scar for the interosseous ligament is absent in both UA 8758 and FMNH PR The distal articular surface is absent in UA 8758, the medial surface is exposed in FMNH PR 2324 and the posterolateral edge in FMNH PR 2326 (Figure 73). The distal end of the ulna is small (about half the size of the proximal end). The anterior

67 320 A. H. Turner Figure 72. UA 8758, Araripesuchus tsangatsangana. Partial right ulna in medial (A), posterior (B), lateral (C), and anterior (D) views. Scale ¼ 1 cm. (Photographs by C. Leonard.) and posterior edges are formed by small convexities separated by a shallow groove. This condition is similar to but not exactly like that seen in Chimaerasuchus paradoxus (Wu and Sues 1996b). The posterior convexity is more pronounced than the anterior convexity and projects out posteriorly from the surface of the bone. The distal radius and the dorsal posterolateral surface of the radiale make contact with the medial surface of the anterior distal ulna. Radius Seven radii were recovered four left (FMNH PR 2298, FMNH PR 2326, FMNH PR 2329, FMNH PR 2339) and three right (FMNH PR 2298, FMNH PR 2324, FMNH PR 2327). In outline, the radius of A. tsangatsangana is a relatively simple bone, elliptical in cross-section at mid-diaphysis and expanded at both ends. The long axis of the proximal articular surface is parallel with that of the distal end. The distal end is angled slightly anteriorly, but not to the extent seen in Alligator. In general shape, the radius is slender and rod-like (Figure 74). Nearing the proximal end but prior to the tuberosity on the anterior margin, the shaft of the radius bends slightly medially away from the ulna. In this respect, the radius of A. tsangatsangana is more similar to that of Dibothrosuchus than it is to modern crocodylians. The radius and ulna of Dibothrosuchus remain in close proximity for most of the distal two-thirds of their lengths. Like Dibothrosuchus, A. tsangatsangana has an ulna that is not as strongly bowed as in modern crocodylians, as well as the medial bending of the radius (Wu and Chatterjee 1993). The proximal articular surface is roughly rectangular in outline. This surface bears a mild concavity a surface corresponding to the radial condyle of the humerus. The lateral margin of this surface is mildly expanded and deflected ventrally for the proximal facet for the ulna. Proximally on the lateral surface of the radius and just inferior to the articular surface, the scar for the common tendon of M. humeroantebrachialis inferior and M. biceps brachii is present (rs1). Distal to this, but still on the proximal half of the radius, a tubercle is present along the posterior margin. This corresponds to the location for the insertion of M. humeroradialis (Fürbringer 1876, Meers 2003). An anteroposteriorly spiraling ridge is located along the lateral surface of the diaphysis (rs2). This ridge marks the lateral margin of the insertion of M. humeroradialis brevis. A ridge for the medial head for the humeroradialis is not present in A. tsangatsangana. Brochu (1992) described a ventral scar that was intersected by the humeroradialis brevis. This appears not to be present in Araripesuchus, although a shallow and slightly roughened area is present near the contact facet for the radiale, which may correspond to the distal-most extent of the ventral scar. Distally, the insertion for M. ulnoradialis is distinct and expressed as a smooth triangular

68 New Araripesuchus from Madagascar 321 Figure 73. Forearm morphology. A, Partially obscured left radius, ulna, ulnare, radiale and pisiform (FMNH PR 2324). B, Nearly complete right forearm. Distal end of humerus damaged as well as the proximal surface of the radius (FMNH PR 2339). Scale ¼ 1 cm. (Photograph in A by C. Leonard. Photographs in B by Mahajangasuchus Ellison.) depression in the bone, as in crocodylians (Brochu 1992). The distal articular surface is slightly damaged in FMNH PR 2329 its anterior margin partially broken. Nevertheless, the surface is mildly convex and appears to be angled to the anterior. The entire surface contacts the radiale. The medial surface of the radius is less interesting. The medial margins of M. humeoradialis medialis and M. humeroradialis brevis do not impress visible correlates upon the radius. Distal to the contact surface for the humerus and near the anterior border of the radius there is a low crest and small tuberosity marking the insertion of M. humeroradialis. Carpus Historically, very little attention has been given to the crocodylomorph carpus. Brochu (1992) suggested this trend may be due to the lack of a unique intracarpal joint in the wrist comparable to the astragalocalcaneal complex. The lack of interest in the carpus, however, could stem from a broader lack of interest in the crocodylomorph forelimb an unfortunate phenomenon, perhaps driven by the absence of an early description of the forelimb musculature comparable to that of Romer s description of pelvic muscles. Either way, the crocodylomorph carpus is interesting. The elongate radiale and ulnare found in modern crocodylians recalls back to the cursorial habit of the ancestral crocodylomorph. In fact, Walker (1970) and Clark (in Benton and Clark 1988) considered the presence of elongate proximal carpals as a synapomorphy of Crocodylomorpha. Four radialia were recovered pertaining to A. tsangatsangana two left (UA 8736, FMNH PR 2324) and two right (UA 8737, FMNH PR 2310), the latter being preserved with its complementary ulnare and epipodials (Figure 73). Like the epipodials, the

69 322 A. H. Turner Figure 74. FMNH PR 2329, Araripesuchus tsangatsangana. Left radius in medial (A), posterior (B), lateral (C), anterior (D), proximal (E), and distal (F) view. Scale ¼ 1 cm. (Photographs by C. Leonard.) radiale is a slender element (Figure 75). The proximal end has three articular surfaces. The largest, comprising the entire proximal surface, is the facet for the radius. The surface is boomerang shaped and mildly concave, with the medial edge of the facet at a lower level than the lateral edge. Laterally and extending at a right angle to the radius facet, there is a roughly rectangular facet for the ulna. The distal portion of the facet tapers to an acute point that is directed anterolaterally and intersects the small and ventrally disposed facet for the ulnare. In anterior view, two rugosities are present near the proximal margin. The lateral rugosity (rds1) lies adjacent to the ulna facet and marks the origin of the extensors for digit II. The medial rugosity (rds2) indicates the attachment of M. extensor carpometacarpus and M. extensor carpophalangei for digit I (Brochu 1992). Given the slenderness of the radiale, these two muscle attachment points lie closer together than in Alligator, resulting in a sulcus between the two. Radialia are known for Notosuchus terrestris (Pol 2005) and Chimaerasuchus paradoxus (Wu and Sues 1996b), and a similar sulcus is seen in these forms although their radialia are stouter than that of A. tsangatsangana. The posterior surface is less complex. The proximal shaft is divided by a median ridge. On either side, the bone is slightly rugose (rds3). These surfaces mark the attachment of M. flexor carpometacarpus and flexor carpophalangei of digit I, M. flexor carpometacarpals of digit II, and the radius-radiale ligament (Brochu 1992).

70 New Araripesuchus from Madagascar 323 Figure 75. Right radiale (FMNH PR 2310) in posterior (A), medial (B), anterior (C), lateral (D), and proximal (E) view. Right radiale (UA 8736) in posterior (F), medial (G), anterior (H), and lateral (I) view. Scale ¼ 1 cm. (Photographs by C. Leonard.) Distally, the articular surface is slightly concave, as in Chimaerasuchus paradoxus and Notosuchus terrestris, and more than likely contacted the centrale, although that carpal element is currently unknown for Araripesuchus. Only three ulnaria were recovered, a small left ulnare complementing the radiale of UA 8736, a small right ulnare complementing the radiale of FMNH PR 2324, and a large right ulnare (UA 8759) whose distal and proximal ends are slightly damaged (Figure 76). The ulnare is shorter than the radiale, slightly longer than two-thirds the length of the radiale. The element is relatively simple, the diaphysis is narrow and each end flares slightly very similar in shape to the radiale but without the lateral and medial processes. The distal surface is wider than the proximal. The proximal surface is very slightly concave for its contact with the pisiform carpal. FMNH PR 2324 preserves the pisiform in a more or less articulated state with the ulnare. Little to no detail, however, can be seen in the pisiform. Like many other aspects of the shoulder and forelimb of A. tsangatsangana, the carpus resembles the more gracile and elongate carpi seen in earlier crocodylomorphs, especially that of Dibothrosuchus. The carpus has been described in few other smallbodied mesoeucrocodylians Chimaerasuchus paradoxus (Wu and Sues 1996b), Uruguaysuchus aznarezi (Rusconi 1933), and Notosuchus terrestris (Pol 2005). The radiale and ulnare in these taxa tend to be stouter and comprise less of the total length of the forelimb, proportionally similar to that seen in Alligator. The carpus of Araripesuchus comprises a larger proportion of the forelimb length than the aforementioned taxa. This, combined with their overall elongate and slender morphology, is more suggestive of the carpus of Dibothrosuchus or Orthosuchus stormbergi (Nash 1975, Wu and Chatterjee 1993). Moreover, the radiale and

71 324 A. H. Turner Figure 76. UA 8736, Araripesuchus tsangatsangana. Left ulnare in anterior (A), medial (B), posterior (C), and lateral (D), view. Scale ¼ 1 cm. (Photographs by C. Leonard.) ulnare of Araripesuchus are considerably longer than the metacarpals, as in Dibothrosuchus or Orthosuchus stormbergi (Nash 1975). Manus Unfortunately, little can be said regarding the manus of A. tsangatsangana. Indeed, this extends to the taxon Araripesuchus in general, seeing as no metacarpal or phalangeal elements have been described for the other Araripesuchus species. A number of metapodials and phalanges were recovered from among the specimen bearing material (FMNH PR 2312, FMNH PR 2328; Figure 77). Given that the majority of this material was isolated, unambiguous assignment to the manus was difficult or Figure 77. FMNH PR 2312, Araripesuchus tsangatsangana. Right metacarpal II and phalanx in anterior (A), medial (B), posterior (C), and lateral (D) view. Scale ¼ 1 cm. (Photographs by C. Leonard.)

72 New Araripesuchus from Madagascar 325 Figure 78. FMNH PR 2328, Araripesuchus tsangatsangana. Partial manus preserved metacarpals II, III, and IV, as well as phalanges associated with digit II. Scale ¼ 1 cm. (Photograph by C. Leonard.) in most cases impossible. FMNH PR 2328 are the only identified metacarpals, this specimen consists of metacarpals II IV, and the three phalanges of MC II. MC IV is slender, but lacks its proximal end. The distal portion terminates in a slight trochlea. MCIIislessslenderthanMCIV.Theproximal end is roughly triangular in cross-section, the medial portion of which thins at its overlap with the proximal-most portion of MC III. The proximal end of MC III is relatively broad and flares medially very slightly. Present on the anterior surface of the proximal end is a shallow triangular depression, medial to which there is another small depression. The distal end is trochleated and the plane of the trochlea rotated laterally slightly resulting in a slight twisted appearance to the metacarpal (Figure 78). The proximal phalanges are longer than the distal and have a distinct midpoint constriction. The proximal articular surface is concave for the reception of the preceding manual element. The proximal concavity is comprised of three conjoined concavities, giving the proximal end a clover appearance in dorsal view. Moving distally, the phalanges become shorter and stouter, ending in a small and slightly recurved ungual phalanx. Pelvic girdle general form and preservation Portions of at least seven pelves (UA , UA , FMNH PR , FMNH PR 2301, FMNH PR 2303, FMNH PR ) in varying states of preservation, were recovered and are referred to Araripesuchus tsangatsangana. FMNH PR 2298 preserves the most complete pelvis with a wellpreserved sacrum attached to complete right and left ilia. The dorsal surface of the sacrum is obscured by matrix and poorly exposed. The ischia and left pubis are not preserved in FMNH PR 2298, though a portion of the right pubis is partially exposed underneath the right hindlimb. The sacrum and right ilium of a larger individual (FMNH PR 2301) lacks the anterior sacral ribs and the ilium is disarticulated from the posterior right sacral rib. FMNH PR 2297 preserves a large but poorly exposed left ilium and a partial pubis. FMNH PR 2303 consists of moderately sized, well-preserved left and right ilia. Also recovered was a partial sacrum (UA 8767), smaller than that of FMNH PR 2301, and a nearly complete left ilium (UA 8768). These two elements, however, were not associated with one another. FMNH PR 2330 is disarticulated, but preserves both ilia, a partial left ischium, and a nearly complete left pubis.

73 326 A. H. Turner Figure 79. FMNH PR 2303, Araripesuchus tsangatsangana. Right ilium in ventrolateral (A), medial (B), and dorsal (C) view. Scale ¼ 1 cm. (Photographs by C. Leonard.) The posterior ilioischiadic contact surface is smooth on the ilium, but the anterior facet remains difficult to characterize given generally poor preservation of the anterior ischiac facet and a paucity of recovered ischia. The smooth facet indicates that the ischium had not fused with the ilium the pervasive condition among crocodylians, though a degree of fusion can be seen in mature individuals (Brochu 1992). The absence of a contact facet on the ilium for the pubis indicates that the pubis did not directly contact the ilium (e.g. A. gomesii, A. patagonicus and other crocodyliforms). The acetabulum is almost completely circular in outline and very deep. Hecht (1991) noted the same condition in A. gomesii (AMNH 24450) and Ortega et al. (2000) in A. patagonicus. Likewise, this same morphology is seen in Notosuchus terrestris (Pol 2005; pers. obs.), Chimaerasuchus paradoxus (Wu and Sues 1996b), and other non-neosuchian crocodyliforms. The acetabulum is overhung by a large supraacetabular crest, suggesting that Araripesuchus possessed or was at least capable of a relatively upright posture. This is consistent with the morphology of the

74 New Araripesuchus from Madagascar 327 Figure 80. FMNH PR 2303, Araripesuchus tsangatsangana. Left ilium in ventrolateral (A), medial (B), and dorsal (C) view. Scale ¼ 1 cm. (Photographs by C. Leonard.) shoulder girdle, which also showed characteristics of erect limb posture. Ilium The ilium (Figures 79 81) bears a well-developed posterior (postacetabular) process, but the anterior (preacetabular) process is greatly reduced as in A. gomesii, A. patagonicus, and other mesoeucrocodylians, e.g. Chimaerasuchus paradoxus (Wu and Sues 1996b), Notosuchus terrestris (Pol 2005), Mahajangasuchus insignis (Buckley and Brochu 1999), Uruguaysuchus aznarezi (Rusconi 1933) and Theriosuchus pusillus (Wu et al. 1996). Clark (1994) considered this trait a synapomorphy for nonprotosuchid crocodyliforms, although this morphology is not present in thalattosuchians. The dorsal surface is striated along its edge, but not as heavily as in crocodylians, and continues onto the posterior facing edge of the posterior process of the ilium. The ilium lacks the developed dorsal iliac blade seen in Alligator, being more similar to that seen in

75 328 A. H. Turner Figure 81. Comparison between ilium size and muscle scarring. A, Ventrolateral view left ilium UA B, Lateral view of partial right ilium FMNH PR Scale ¼ 1 cm. (Photographs by C. Leonard.) other mature non-crown group crocodyliforms and immature Alligator (Brochu 1992). The ilium bears a deep acetabulum, which comprises the entire surface of the ilium below the prominent supraacetabular crest. A nutrient foramen is found on the right ilium of FMNH PR 2301 on the posterior process, immediately outside of the acetabulum (Figure 81). The acetabulum is perforated ventrally between the anterior and posterior peduncles. A scar for the teres ligament is visible on UA 8768 and FMNH PR The posterior peduncle is larger than the anterior one, with contact facets are smooth on both. The anterior peduncle is poorly preserved on most ilia UA 8768 retains a nearly intact peduncle that is comparable to A. gomesii. The anterior process is well preserved in UA 8768 and FMNH PR The structure is greatly reduced as in Notosuchus terrestris (Pol 2005), Chimaerasuchus paradoxus (Wu and Sues 1996b), Theriosuchus (Wu et al. 1996), Uruguaysuchus aznarezi (Rusconi 1933) and Mahajangasuchus insignis (Buckley and Brochu 1999). The process is located dorsal to, but nearly in line with, the anterior peduncle. Living crocodylians also have a reduced anterior process (Mook 1921), however, the process lies posterior to the anterior peduncle, dorsal to the acetabular perforation (e.g. Alligator; FMNH ) (Figure 80). Although small, the anterior process is very prominent, forming a triangular prong on the anterodorsal surface of the ilium. Both A. gomesii

76 New Araripesuchus from Madagascar 329 (AMNH 24450) and A. patagonicus (MUC PV 267) have this same prong -like anterior process, as does Mahajangasuchus insignis (UA 8654) and Theriosuchus (Wu et al. 1996; IVPP V10613). The anterior processes of Notosuchus terrestris (Pol 2005) and Chimaerasuchus paradoxus (Wu and Sues 1996b) are not shaped like A. tsangatsangana, and Rusconi (1933) did not figure Uruguaysuchus aznarezi as possessing a prong -like process. The surface of the process is rugose and may mark the origin of M. iliocostalis (Romer 1923) (Figure 81). The posterior process is elongate, comprising slightly more than one-third the total length of the ilium. Ancestrally, it appears that in crocodylomorphs this process was directed posteriorly without any dorsal or ventral deflection (e.g. Dibothrosuchus and Terrestrisuchus). In some basal crocodyliforms (e.g. Chimaerasuchus paradoxus (Wu and Sues 1996b), Notosuchus terrestris (Pol 2005), Orthosuchus stormbergi (Nash 1975) and Uruguaysuchus aznarezi (Rusconi 1933) the process is directed posteroventrally. In the smaller ilia of A. tsangatsangana (FMNH PR 2303, UA 8768) the process appears to have a slight posteroventral aspect. This may be due, however, to a small ventral projection on the posterior-most portion of the process combined with a slight curve on the dorsal margin of the posterior process. In the larger specimen (FMNH PR 2301; Figure 81B), the process is, as a whole, dorsoventrally broader with the ventral projection at the end of the process less pronounced and the curve of the dorsal surface nearly absent. A similar condition is seen the A. gomesii (AMNH 24450) and A. patagonicus (MUC PV 267), therefore, I interpret the posterior process of the ilium in Araripesuchus to be directed posteriorly without any dorsoventral deflection. Pol (2005) noted a dorsomedial twist in the posterior process of the ilium in Notosuchus. A similar morphology is present in the ilia of A. tsangatsangana as well as in A. gomesii and A. patagonicus. The process, as it originates near the supraacetabular crest, faces ventrolaterally. The process twists along its length to face dorsolaterally for approximately the final half of its length. The medial surface of the ilium is predominantly smooth, with only a few light striations on the end of the posterior process. The facets for the two sacral ribs are preserved on the right ilium of FMNH PR 2303 (ss1 and ss2). The posterior facet is the longer of the two and occupies nearly two-thirds of the surface of the ilium. Although the anterior facet surface is less well preserved, its semicircular outline can still be distinguished. The two contact facets do not contact one another and are separated by about a half of a centimeter. In lateral view, muscle attachment scarring is visible along the dorsal margin. In smaller specimens, scarring is less distinct than in larger individuals. A depression is present on the posterior margin of the supraacetabular crest that corresponds to the origin of M. iliofemoralis (Romer 1923). The rugosity along the margin of the supraacetabular crest is the largest of the scars and corresponds to the origin of M. iliotibialis (Romer 1923). Carrano and Hutchinson (2002) depict a large attachment surface for the second head (M. iliotibialis 2) of this muscle in Alligator. The first (M. iliotibialis 1) and third (M. iliotibialis 3) heads have smaller, more circular attachments anterior and posterior, respectively, to that of the second head. A distinct M. iliotibialis 1 scar cannot be discerned in the present taxon. Posterior to the supraacetabular crest there is an ovular concavity that may be the scarring related to M. iliotibialis 3. This region, however, corresponds topographically to the area for the origin of M. iliofibularis (Romer 1923, Carrano and Hutchinson 2002) that can be seen in older crocodylians (Brochu 1992). It appears in some specimens (FMNH PR 2301 and UA 8768) that a division is present in the depression, and may indicate that the scar is common to both iliofibularis and iliotibialis 3 muscles. The posterior process bears two muscle scar sites. The more dorsal of the two is situated on the end of the process. It is U -shaped, with the bottom of the U directed ventrally at a 458 angle. In the larger ilium (FMNH PR 2301), the scar is very prominent and bounded ventrally by an enlarged rim. A. gomesii (AMNH 24450) bears a similar scar, but the presence of such a scar in A. patagonicus (MUC PV 267) cannot be determined due to poor preservation of the cortical bone. Romer (1923), as well as Carrano and Hutchinson (2002), figured this area as the attachment surface for head two of the flexor tibialis internus (FTI2) and externus (FTE). In Alligator (FMNH ; Brochu 1992), the FTI and FTE attach further forward on the posterior process, leaving a smooth unscarred end on the process. The condition in Araripesuchus differs from this, with the flexor tibialis scar at the posterior end of the process. The origin of M. caudofemoralis (coccygeofemoralis) brevis is located on the ventral surface of the posterior process (Romer 1923, Carrano and Hutchinson 2002). This attachment surface is developed as a flange that projects posteroventrally from the ilium. The flange is proportionally larger in the large specimen (FMNH PR 2301). Where it projects from the ilium, a notch is present between it and the remainder of the ilium. A similar notch is figured by Rusconi (1933: fig. 36) for Uruguaysuchus aznarezi. Mahajangasuchus insignis possesses a notch on the end of the posterior process, but this is located higher on the ilium and may simply reflect a larger attachment surface for the caudofemoralis. In Theriosuchus (Wu et al. 1996; IVPP V10613) the caudofemoralis scar is positioned more anteriorly on the ventral surface of the posterior process of the ilium than in Araripesuchus (i.e. more like the condition seen in Alligator). Though the

77 330 A. H. Turner Figure 82. FMNH PR 2330, Araripesuchus tsangatsangana. A, Left ischium, lateral view. B, Left ischium, medial view. Scale ¼ 1 cm. (Photographs by C. Leonard.) surface is moderately developed ventrally, no notch is present between it and the remainder of the ilium. Ischium Interestingly, only one ischium appears to have been preserved (Figure 82). It is largely intact, though laterally a portion of the distal blade could not be completely cleaned of matrix. The blade is broken around midshaft and missing its distal-most end. The proximal end is largely intact with only the proximal ends of the iliac processes damaged. The ischium of A. tsangatsangana is typical of most crocodyliforms as it possesses a pair of proximal processes that contact the ilium and a distally expanded blade, which curves medially to a greater or lesser extent. Ischia from Araripesuchus are not well described given that A. patagonicus does not preserve them and the only known ischium from A. gomesii (AMNH 24450) has a fracture running proximodistally through it (Hecht 1991). Overall, the ischium is slender and mediolaterally thin, with the iliac processes less massive than in neosuchians like Theriosuchus (Wu et al. 1996) and Alligator (Mook 1921; pers. obs. FMNH ). The processes do not diverge symmetrically from the blade of the ischium, a condition similar to that of Mahajangasuchus insignis and Alligator, but contrasting the condition in Chimaerasuchus paradoxus (Wu and Sues 1996b). The anterior iliac process diverges from the anterior margin of the ilium. The proximal end of the process is broken, but the remaining shaft is generally cylindrical in shape, projecting anteriorly with little dorsal inclination as the process contacts the ilium. In A. gomesii (AMNH 24450), the anterior process is long and cylindrical, ending in an enlarged spherical head like in Mahajangasuchus insignis (Buckley and Brochu 1999). Both Chimaerasuchus paradoxus (Wu and Sues 1996b) and Uruguaysuchus aznarezi (Rusconi 1933; Figure 18) lack this cylindrical process with an enlarged spherical head. In A. tsangatsangana, the contact for the pubis is located on the ventral surface of the anterior process, indicating that the pubis was completely excluded from the acetabulum. The posterior process is largely unpreserved in A. tsangatsangana, rendering the morphology of the element difficult to evaluate. It is unclear whether a distinct acetabular surface is present on the posterior process. The lateral surface of the ischium serves as the attachment surface for the origin of a number of limb muscles. On the anterolateral side of the ischium, below the anterior iliac process, there is a shallow pit related to the origin of M. puboischiotibialis. The posterolateral side of the ischial blade serves as the origin for head two of M. adductor femoris (Romer 1923). A distinct rugosity is not present on the bone, although a set of striations is present and likely marks the origin of this muscle. In most crocodylomorphs, the posterior margin of the ischium ventral to the posterior iliac process bears scarring related to the origin of head three of M. flexor tibialis internus. No such scar is discernable in FMNH PR 2330, which is interesting because a scar for this muscle is present even in hatchling Alligator

78 New Araripesuchus from Madagascar 331 Figure 83. FMNH PR 2331, Araripesuchus tsangatsangana. A, Left pubis, ventrolateral view. B, Left ischium, dorsomedial view. Scale ¼ 1 cm. (Photographs by C. Leonard.) (Brochu 1992). The medial surface of FMNH PR 2330 is less well exposed. A set of small striations are present on the dorsal margin of the posterior iliac process that is likely associated with the origin of M. puboischiofemoralis internus (Romer 1923, Rowe 1986). Pubis The pubis is generally paddle-shaped in outline (Figure 83). Proximally, the bone lacks an obturator foramen and consists of a slender nearly cylindrical neck, which expands into a flat, triangular blade distally. As described earlier, the pubis articulates with the ischium and is therefore excluded from the acetabulum. This feature has been previously considered a synapomorphy for Eusuchia (Clark in Benton and Clark 1988, Norell and Clark 1990). It now appears, however, that this apomorphy occurred earlier within crocodyliforms, e.g. Chimaerasuchus paradoxus (Wu and Sues 1996b), Uruguaysuchus aznarezi (Rusconi 1933), Mahajangasuchus insignis (Buckley and Brochu 1999), Sunosuchus (Wu et al. 1996). The pubis is interesting because the shaft of the pubis is slightly flattened proximally and rotated medially from the plane of the blade. In Alligator, the pubic blade faces dorsally with the shaft of the pubis extending posteriorly to contact the ischium. The pubic shaft, however, is not rotated mediolaterally at all in Alligator. In A. tsangatsangana, the blade of the pubis and the flattened portion of the shaft oppose one another at roughly a 458 angle. The flattened portion of the shaft extends out towards the blade as a distinct ridge for about the first one-third of the length of the pubis before it softens into the blade (Figure 83). The ischiadic contact surface is broken and missing in all specimens except FMNH PR 2330 and FMNH PR 2331, with the surface of the latter being damaged slightly. Where preserved, the surface is smooth and roughly oval in shape. The two pits present on the articular surface in Alligator (Brochu 1992) are not present in Araripesuchus. As in crocodylians (Romer 1923, Brochu 1992, Carrano and Hutchinson 2002), much of the blade served as attachment surface for the two heads of M. puboischiofemoralis externus (PIFE1 and PIFE2). Distinction among the muscles scarring along the articular end of the pubis proves more problematic. Anteromedially, there is a shallow rugosity corresponding topographically with the site of attachment for head two of M. ambiens (Romer 1923, Carrano and Hutchinson 2002), as well as the point of attachment for a pubis-ischium ligament described by Brochu (1992). Distinction between or exclusion of one of these possibilities cannot be made for A. tsangatsangana based on the preserved material. Due to the slight flattening of the pubic shaft and its rotation in relation to the pubic blade, the attachment surface for head one of M. ambiens is located on the ventrolaterally facing surface on the ridge of the pubis. Hindlimbs general form and preservation Numerous femora, tibiae, and fibulae are preserved. Four left and four right femora were recovered (UA 8734, FMNH PR 2297, FMNH PR 2298, FMNH PR 2300, FMNH PR 2330, FMNH PR 2337), although not all of these were paired and are, therefore, indicative of more than four individuals. Three left and four right tibiae (FMNH PR 2298, FMNH PR 2300, FMNH PR 2330, FMNH PR 2335, FMNH PR 2337) and three right and two left fibula (UA 8781, FMNH PR 2298, FMNH PR 2300, FMNH PR 2330, FMNH PR 2335) were also recovered. FMNH PR 2298 preserves partial but articulated left and right hindlimbs. The right femur is damaged midshaft and much of the left femur remains obscured by matrix. The left tibia is broken proximally and distally and the left fibula is not present. FMNH PR 2297 and FMNH PR 2337 preserved the proximal half of a left and right femur, respectively and FMNH PR 2335 consists of a poorly preserved distal right femur. FMNH PR 2300 preserves the largest and most intact hindlimb complement. Although fractured in a number of places, these hindlimb elements are very well preserved with only the femur lacking a small portion on its distal articular surface.

79 332 A. H. Turner FMNH PR 2330 possesses well preserved, but partial, left and right femora. The right femur is obscured distal to the fourth trochanter. The left femur is more intact, lacking only the head. Only the proximal end of the left tibia is preserved, but the left fibula is more complete, preserving all but its distal end. Tarsal elements are more rare. FMNH PR 2330 preserves the distal articular surface of a right astragalus. A calcaneum is present in FMNH PR 2297 and is well preserved. The metatarsus is represented by a number of specimens. A metatarsus (FMNH PR 2319) consisting of the distal half of metatarsals II, III and IV was recovered. FMNH PR 2330 preserves two metatarsals, FMNH PR 2338 preserves an isolated metatarsal IV, and UA 8780 consists of the second metatarsal. FMNH PR 2337 preserves a nearly complete pes. Femur The femur is a long and gracile bone (Figure 84). Like most crocodyliforms, the femur is generally sigmoid in shape, though not so strongly sigmoid as Alligator and other neosuchians (i.e. more similar to crocodyliforms such a Notosuchus terrestris and Uruguaysuchus aznarezi and basal crocodylomorphs like Terrestrisuchus gracilis). This stems from the fact that distal to the constriction between the femoral head and fourth trochanter, the shaft is much straighter than in neosuchians like Alligator (FMNH ), Sunosuchus (Wu et al. 1996), Pachycheilosuchus trinquei (Rogers 2003), and Terminonaris robusta (Wu et al. 2001). Moreover, the femora of A. tsangatsangana lack the constriction at the level of the puboischiofemoralis internus scars. Notwithstanding, the femoral head is still expanded and bent anteromedially at nearly a 258 angle. The distal end is expanded and forms two distinct condylar surfaces (FMNH PR 2298). The lateral condyle is slightly larger than the medial and possesses a very subtle fibular condyle. A shallow groove delimits the fibular condyle from the remainder of the lateral condylar surface. The shaft of the femur is twisted along its long axis resulting in the planes of the proximal and distal condyles being offset from one another. This offset is large in crocodylians (roughly 658; Parrish 1986), but in A. tsangatsangana this offset is only around 458. Figure 84. FMNH PR 2300, Araripesuchus tsangatsangana. Left femur in lateral (A), posterior (B), medial (C), and anterior (D) view. Scale ¼ 1 cm. (Photographs by C. Leonard.)

80 New Araripesuchus from Madagascar 333 Figure 85. FMNH PR 2300, Araripesuchus tsangatsangana. Muscle attachment scar associated with fourth trochanter (t 4 ). CFL, caudofemoralis longus; CFB, caudofemoralis brevis; PIFI 1, puboischiofemoralis internus 1. (Photograph by C. Leonard.) The fourth trochanter (t 4 ) is well developed and prominent on the medial surface of the femur (Figure 85). It is located close to the femoral head, less than one quarter of the way down the shaft of the femur. The surface of the trochanter is rugose (tr 1, tr 2 ), and it is bordered on either side by depressions. The rugosity posterior to the trochanter is weakly crescent shaped and corresponds to the insertion of M. caudofemoralis brevis (Romer 1923, Brochu 1992, Carrano and Hutchinson 2002). The depression anteromedial to the trochanter is very broad and nearly circular in outline (cdfemf). The depression is located on a very prominent flange or process that extends anteriorly from the shaft of the femur (character 103-1; Figure 94). The surface of the depression is finely striated and the edge of the flange is rugose. A similar structure is present in the other Araripesuchus species (A. gomesii AMNH 24450; A. patagonicus MUC PV 267) as well as in Notosuchus terrestris (Pol 2005), Mahajangasuchus insignis (Buckley and Brochu 1999), and Uruguaysuchus aznarezi (Rusconi 1933). The rugose surface of the trochanter, and at least a portion of the anterior flange, serves as the insertion point for M. caudofemoralis longus (Romer 1923). Pol (2005) and Buckley and Brochu (1999) have interpreted this structure as serving solely for the insertion of caudofemoralis longus (CFL; coccygeofemoralis sensu the previously mentioned authors). The muscle insertions onto the flange may prove more complex (Figure 85). Romer (1923), Fauvel (1879), and Carrano and Hutchinson (2002) figure M. puboischiofemoralis internus 1 (PIFI 1) inserting anteriorly and distally to M. caudofemoralis longus on the femoral shaft. The PIFI 1 insertion forms a slightly crescent shaped surface anteriorly to CFL. Brochu (1992) figured the insertion of PIFI 1 differently in A. mississippiensis (PIFI M sensu Rowe 1986 and Brochu 1992), with PIFI 1 being distal to the insertion of CFL and completely separate from the scar. If Brochu s (1992) interpretation is correct than it is likely that the flange in Araripesuchus, Mahajangasuchus insignis, Notosuchus terrestris, and Uruguaysuchus aznarezi has been correctly interpreted and served simply as the attachment for CFL. This would, therefore, indicate an enlargement of the CFL attachment surface relative to the fourth trochanter and an anterior movement of the insertion for this primary femoral retractor. It is not unreasonable, however, to consider the anterior flange as a common attachment surface for both CFL and PIFI 1 given the conclusions of Romer (1923) and Carrano and Hutchinson (2002). The location of the flange and the rugosity of its margin are consistent with this interpretation. If this is the case, then this structure would indicate that both the CFL and PIFI 1 saw an anterior shift in their insertion in the taxa discussed above. The function of PIFI 1 remains ambiguous, although it appears to create (along with PIFI 2) some ancillary whole-limb adduction during the swing phase in modern crocodylians (Hutchinson and Gatesy 2000). The anterior displacement of the flange likely resulted in increased medial rotation during CFL contraction and the size of the flange may mark on increased PIFI 1 size and overall adduction capability. Proximal to the anterior flange, on the lateral surface of the femur, is a set of muscle scars indicating the insertion of M. puboischiofemoralis internus 2 (PIFI 2; Romer 1923). The two scars, one proximally (rf2) and one distally (rf1), are spaced farther apart than in Alligator (Brochu 1992). Associated with PIFI 2 scars, and positioned near the center of the lateral surface of the femur, is a raised and rugose tuberosity. This corresponds to the structure that Brochu (1992) termed the proximal dorsal tuberosity. Immediately distal to the femoral head, along the posterior surface of the femur, is a striated depression bordered laterally by a slightly rugose ridge (t G ). This area marks the insertion of M. puboischiofemoralis externus (PIFE; Romer 1923, 1986, Carrano and Hutchinson 2002). Nomenclature for this structure is mixed. Crush (1984) referred to it as a trochanter, while Romer (1956) and Brochu (1992) declined the use of trochanter because the structure is not a tubercle. Topographically, this surface corresponds to the greater trochanter in other archosaurian clades and as such Hutchinson and Gatesy (2000) reference

81 334 A. H. Turner this surface in crocodylians, parenthetically, as greater trochanter. Alligator femora are marked by a number of proximodistally running ridges. The femoral shaft in Araripesuchus tsangatsangana possesses only two proximodistal ridges. Two scars beginning near the PIFI 2 scars, denote the insertions of M. iliofemoralis in Alligator (Romer 1923). Only one such ridge is present in Araripesuchus tsangatsangana. It is located along the anterolateral surface of the femoral shaft and extends farther down the femur than in Alligator. The iliofemoralis ridge is not distinct proximally, becoming more prominent distally and curving laterally towards the condyle. A second longitudinal ridge runs on the posterior of the femur. The ridge begins near the fourth trochanter and diminishes distantly prior to the expansion of the condyles. Romer (1923) interpreted this structure as marking the boundary between the insertion of M. adductor femoris and the origin of M. femorotibialis internus. Brochu (1992) referred to the ridge as the primary adductor scar and noted its early appearance in hatchling crocodylians. The distal articular condyle is developed into distinct lateral and medial hemicondyles and forms a well-developed trochlea. The distal is damaged in FMNH PR 2300 and heavily fractured in FMNH PR 2297 making it difficult to discern distinct muscle attachment scarring. The condylar surfaces appear rugose and a small tubercle is present on the lateral condylar surface just proximal to the fibular condyle, which represents the origin of M. gastrocnemius (Brochu 1992, Carrano and Hutchinson 2002). Tibia The tibia of Araripesuchus tsangatsangana (Figure 86) is similar to those of modern crocodylians as well as other basal mesoeucrocodylians such as Mahajangasuchus insignis (Buckley and Brochu 1999), Uruguaysuchus aznarezi (Rusconi 1933) and Notosuchus terrestris (Pol 2005). The bone is long and slender with a very slight anteroposterior curve in its shaft. The proximal end is expanded as it forms the contact surface for articulation with the femoral condyles. The medial articular surface is larger than the lateral and extends proximally to a greater extent than the medial surface. The proximal end in FMNH PR 2300 lacks the distinct proximal pit noted by Brochu (1992) in crocodylians. Proximally, the anterior edge serves as the insertion for the common tendon of M. iliotibialis, M. femorotibialis, and M. ambiens (Romer 1923). The surface is damaged in FMNH PR 2300, but is well preserved on the right tibia of FMNH PR 2298 illustrating its rugose surface. Just distal to this surface, the tibia is marked by two small, inconspicuous tuberosities. One indicates the insertion of M. flexor tibialis internus (interior sensu Romer 1923, Brochu 1992). This tuberosity is positioned on the anterior surface of the tibia, slightly medial from the midline of the shaft. The scar is proximodistally elongate and is not as distinct, nor as sharply raised from the tibial shaft, as it is in Alligator (FMNH ; Brochu 1992). The more lateral of the tuberosities is immediately distal to the proximal articular surface. This indicates the insertion of M. tibialis anterior. As with the flexor tibialis internus scar, the scarring associated with the tibialis anterior is not prominent and is much weaker than that seen in crocodylians, and more similar to the condition in Mahajangasuchus insignis (Buckley and Brochu 1999). The lateral surface of the tibia, near the proximal end, bears a shallow depression bordered anteromedially by a small ridge. The depression is slightly damaged, along with a portion of the anterior border in FMNH PR 2300, but FMNH PR 2298 preserves the structure completely, illustrating the presence of the ridge even in smaller individuals. This ridge sits just proximally to the insertion scar for the tibialis anterior. The shaft of the tibia is nearly circular in crosssection, with only the lateral edge (facing the fibula), being slightly flattened. The shaft is smooth and devoid of any muscle scarring typically present along the shaft that would correspond to the interosseus cruris insertion and the flexor digitorum longus origins. A small nutrient foramen pierces the lateral surface of the tibia near midshaft. Distally, the tibia expands to form the contact surface with the astragalus. Viewed distally, the surface is crescentic with the medial margin more strongly developed than the lateral. Additionally, the medial portion of the astragalar surface projects distally to a greater extent than the lateral portion. The edge facing the fibula projects laterally, giving the distal lateral margin of the tibia a curved appearance. The posterior surface of the distal tibia bears a triangular depression between the medial and lateral edges of the astragalar contact face. The anterior surface of the distal tibia bears a smooth circular depression, centered between the medial and lateral distal articular surfaces, which corresponds to the attachment of medial tibioastragalar ligament (Brochu 1992). Fibula FMNH PR 2300 preserves a complete right fibula (Figure 87). The element is very long and slender with a very distinct proximal head. The fibula of A. tsangatsangana differs from that of modern crocodylians and other mesoeucrocodylians. The fibular head is mediolaterally compressed and strongly developed posteriorly, producing a sharp bend to the proximal fibula when view in lateral aspect. The broad lateral surface of the flaring proximal head serves as the attachment of the

82 New Araripesuchus from Madagascar 335 Figure 86. FMNH PR 2300, Araripesuchus tsangatsangana. Right tibia in posteromedial (A), lateral (B), anterolateral (C), proximal (D), and distal (E) view. Scale ¼ 1 cm. (Photographs by C. Leonard.) long lateral ligament (Brochu 1992). Alligator (FMNH ), Sunosuchus (Wu et al. 1996), Mahajangasuchus insignis (Buckley and Brochu 1999), and Uruguaysuchus aznarezi (Rusconi 1933: fig. 22) all show a slight posterior expansion and bend to the proximal fibular head. The posterior bend, however, is weak in these other taxa and dissimilar from the morphology of A. tsangatsangana (Figure 98). A. gomesii and A. patagonicus possess fibular heads similar to A. tsangatsangana. This feature appears unique to Araripesuchus though A. wegeneri does not preserve any fibulae. The iliofibularis trochanter (anterior trochanter of Sereno 1991) is a distinct feature on the lateral surface of the fibula. The trochanter is a smooth, proximodistally elongate ridge located on the fibular head, very near the proximal margin. An inconspicuous wrinkle on the bone extends from the trochanter to contact the proximal edge of the fibula. The location of the iliofibular trochanter is not typical for crocodyliforms it is

83 336 A. H. Turner Figure 87. FMNH PR 2300, Araripesuchus tsangatsangana. Right fibula in lateral (A), posterior (B), medial (C), anterior (D), proximal (E), and distal (F) view. Scale ¼ 1 cm. (Photographs by C. Leonard.) generally located about one quarter of the length down the shaft of the fibula (e.g. Alligator and Mahajangasuchus and numerous other archosauriforms [Sereno 1991]). Immediately anterior to the iliofibularis trochanter, there is a thin flange along the anterior margin of the fibula. Although the bone is not rugose on the flange, the structure corresponds to the origin of M. flexor digitorum longus (Brochu 1992). The shaft of the bone is slender and compressed mediolaterally. Generally, the shaft is smooth and devoid of distinct muscle scarring, though a small nutrient foramen is present medially near midshaft. Close examination reveals subtle wrinkling on the medial surface distal to the fibular head. This site likely indicates the origin of M. tibialis posticus (Brochu 1992). The distal two-thirds of the fibula (the portion facing the tibia) is very flattened, forming a sharp anterior edge to the fibula and a sharp crease on the posteromedial surface of the bone. This surface faces more anteriorly than the proximal portion of the shaft giving the shaft of the fibula a twisted appearance. The distal end of the fibula is enlarged and triangular in cross-section, but lacking a distal hook (sensu Brochu 1992) like that seen in Alligator.

84 New Araripesuchus from Madagascar 337 Figure 88. FMNH PR 2297, Araripesuchus tsangatsangana. Left calcaneum in anterior (A), lateral (B), posterior (C), medial (D), dorsal (E), and ventral (F) view. Right astragalus in ventral view (G). Scale ¼ 1 cm. (Photographs by C. Leonard.) The distal end displaced anterolaterally from the main axis of the fibular shaft by about 58. Proximal to the end of the fibula, there is a tubercle on the posteromedial surface. This tubercle is associated with the origin of M. interosseus cruri (Brochu 1992). Tarsus general form and preservation In contrast to the carpus, a vast amount of work has been conducted on the morphology and systematic significance of the archosauriform tarsus (Cruickshank 1979, Brinkman 1980, Chatterjee 1982, Hecht and Tarsitano 1984, Parrish 1986, Sereno 1991, Brochu 1992). The tarsal morphology of Araripesuchus tsangatsangana as well has other crocodylomorphs, consists of the crocodile normal condition (Bonaparte 1971, Chatterjee 1978). This morphology consists of a peg on the astragalus that fits into a socket on the calcaneum. This allows for rotational motion of the calcaneum and pes relative to a stationary astragalus and tibia. The Araripesuchus tsangatsangana preserves two astragalus (FMNH PR 2297, FMNH PR 2330), still partially contained within rock matrix, and exposing only the posterior surface of the elements. Two wellpreserved calcanea were also recovered (FMNH PR 2297 and FMNH PR 2298). Neither of these specimens preserve the tarsus articulated or with tarsal elements articulated to the tibia or fibula. Moreover, no distal tarsal elements were recovered for the taxon. Astragalus The distal surface of the astragalus is very similar to other crocodyliforms (Figure 88G). It is comprised of

85 338 A. H. Turner two distinct surfaces the medial distal roller (Cruickshank 1979, Hecht and Tarsitano 1984) and the astragalar trochlea (Hecht and Tarsitano 1984). The medial distal roller is the articular surface for metatarsals I, II and the third distal tarsal element. A portion of the anterior surface is exposed revealing a squarish fossa the anterior hollow of Hecht and Tarsitano (1983). Protruding and continuing laterally from the distal roller, is the astragalar trochlea. Posteriorly, a deep groove divides the distal roller from the trochlea. This groove supplies the space through which the tendon of M. flexor digitorum longus passes (Brochu 1992). A second groove, slightly deeper than what is seen in Alligator, divides the two surfaces more anteriorly. This groove marks one of the attachments for the metatarsal-distal tarsal ligaments (Brinkman 1980, Brochu 1992). The astragalar trochlea, which forms the peg that inserts into the calcaneum, has sub-parallel sides, but this peg does not taper towards the lateral margin unlike the condition in Alligator. Calcaneum FMNH PR 2298 preserves a complete isolated left calcaneum (Figure 88). Like the astragalus, this element is very similar to that of other crocodyliforms. Compared to Alligator calcanea, the calcaneum of Araripesuchus tsangatsangana is a mediolaterally narrower element, resembling the calcaneum of Uruguaysuchus aznarezi (Rusconi 1933: fig. 24). The calcaneum can be divided into three distinct parts (Brinkman 1980, Brochu 1992) the astragalar peg, an anterior ball, and the posteriorly directed tuber. The anterior ball is mediolaterally narrow, with twothirds of the tibial contact surface rounded and smooth and the remaining one-third forming a flattened ventrally-directed surface for contact with the distal tarsal IV (Brinkman 1980, Brochu 1992). The medial surface of the ball bears a deep socket for the reception of the astragalar peg. This socket is roughly square shaped. Relative to the size of the calcaneum, the socket is very large and deep as in Mahajangasuchus insignis (Buckley and Brochu 1999). This leaves the surrounding bone of the ball thinner than what is seen in Alligator (FMNH ). The lateral surface is smooth and appears pierced by a small nutrient foramen. Medial to the calcaneal socket is a trough-shaped facet upon which the astragalar trochlea articulates. The trough faces anteriorly while medially the trough bends posteriorly, extending past the medial margin of the calcaneal tuber. The tuber is very narrow consistent with the overall morphology of the calcaneum and similar to the condition present in Uruguaysuchus aznarezi (Rusconi 1933). The medial and lateral edges of the tuber are high sided and prominent, forming a deep central groove or sulcus the deep groove of Hecht and Tarsitano (1983). Uruguaysuchus aznarezi possess a similarly high sided and deep groove on the tuber. The calcaneal (Achilles ) tendon passes through this groove in modern crocodylians but does not attach to it (Hecht and Tarsitano 1983, Brochu 1992). Medially, very little bone separates the tuber from the posterior surface of the trough. Ventrally, it appears that the margins of the two structures are nearly confluent with one another. No calcaneum is known for Araripesuchus patagonicus, precluding a comparison with that taxon. Calcanea are known from Araripesuchus gomesii (AMNH 24450) and are very similar to Araripesuchus tsangatsangana. The proportions of the anterior ball and tuber are similar between the two species. The tuber of Araripesuchus gomesii bears a deep posterior groove like that of Araripesuchus tsangatsangana, however, it is unclear if the element is as strongly compressed mediolaterally as it is in A. tsangatsangana. Nevertheless, A. gomesii does possess a calcaneum narrower than Alligator (FMNH ; Brochu 1992). Pes Like the manus, the pes is poorly represented in Araripesuchus tsangatsangana. Unlike the manus, pes are better known in other Araripesuchus taxa i.e. A. gomesii (AMNH 24450). Two partial pes (FMNH PR 2319, FMNH 2337) are preserved along with isolated metatarsals (MT) and phalanges in varying degrees of completeness (UA 8736, UA 8780, FMNH Figure 89. Metatarsal morphology. A, Left metatarsal III (FMNH PR 2338). Anterior on the left and posterior on the right. B, Left metatarsal II (UA 8780). Anterior on the left and posterior on the right. Scale ¼ 1 cm. (Photographs by C. Leonard.)

86 New Araripesuchus from Madagascar 339 Figure 90. Pedal morphology. A, Partial pes (FMNH PR 2319) showing the metatarsals (on the left) and phalanges (on the right). B, Partial right pes (FMNH PR 2337). Scale ¼ 1 cm. (Photographs by C. Leonard.) PR 2330, FMNH PR 2337). Unambiguous assignment of many of these elements proves difficult given this level of preservation. Details of specific elements are therefore based solely on those elements that are complete and clearly assignable. Generally, the metatarsals are slender and very long slightly more than half the length of the tibia. UA 8780 preserves a large MT II and FMNH PR 2338 a MT III (Figure 89). The proximal articular surface is expanded into a fan-shaped surface. Laterally, this surface is nearly as thick as the main shaft of the metatarsal, while medially the proximal surface thins noticeably into a distinct lamina that underlies the proximoposterior surface of the preceding metatarsal. In MT II, nearly two-thirds of the proximal surface forms the thin lamina, while in MT III only the medial half of the proximal surface is thinned into the articulating surface. The shafts of the metatarsals are nearly circular in cross-section. The distal ends are trochleated and the plane of the trochlea rotated laterally slightly resulting in a slight twisted appearance to the metatarsal. Anteriorly, a depression is present above the trochlea, with the posterior surface curving gently into the body of the trochlea. Figure 91. FMNH PR 2314, Araripesuchus tsangatsangana. Pedal phalanges in dorsal (left) and ventral (right) views. Scale ¼ 1 cm. (Photographs by C. Leonard.) The proximal pedal phalanges are longer and more robust than the distal, having a distinct midpoint constriction (FMNH PR 2311; Figure 90). The proximal articular surface is concave for the reception of the preceding pedal element. The proximal concavity is comprised of three conjoined concavities, giving it a clover appearance in proximal view. Moving distally, the phalanges become shorter and more stout ending in a small and slightly recurved ungual phalanx (Figure 91). Dorsal armor general form and preservation Few dorsal armor elements are preserved for Araripesuchus tsangatsangana. Two osteoderms were recovered (FMNH PR 2333). One of the osteoderms preserves both dorsal and ventral surface but is damaged in places, while the other exposes only the ventral surface of the bone. Given their general Figure 92. FMNH PR 2333, Araripesuchus tsangatsangana. Two disarticulated osteoderms, showing ventral and dorsal morphology. Scale ¼ 1 cm. (Photograph by C. Leonard.)

87 340 A. H. Turner outline, the preserved osteoderms are likely from the anterior rows of the dermal armor. Osteoderms These elements are rectangular, and lack the anterolateral process seen in basal crocodyliforms (e.g. Protosuchus richardsoni and Hsisosuchus chungkingensis). The surface of bone is heavily sculpted (Figure 92). The presence of a longitudinal ridge as in Araripesuchus gomesii and Notosuchus terrestris cannot be determined given the damage to that surface in the preserved elements. Orientation patterns cannot be determined for A. tsangatsangana because the two osteoderms are not preserved articulated and associated with an articulated vertebral column. The anterior margin of the osteoderm is smooth, indicating the surface of overlap by the preceding osteoderms. The ventral margins of the osteoderms are concave medially and become less so toward the lateral margin of the elements. Two grooves run mediolaterally on the ventral surface of the osteoderm, with the posterior of the two being marked by subtle striations. Phylogenetic placement Dataset, character coding, and taxon sampling A dataset of 129 morphological characters, with the addition of two new characters, was gathered from previous studies (Clark 1994, Ortega et al. 1996, Gomani 1997, Wu et al. 1997, Buckley and Brochu 1999, Buckley et al. 2000, Pol 2003, Sereno et al. 2003, Turner 2004, Turner and Calvo 2005). The dataset was adapted primarily from Buckley et al. (2000), which is in turn based largely upon the matrix by Clark (1994). These characters were scored across 32 taxa. The taxon-sampling regime was derived from Buckley et al. (2000) and Turner and Calvo (2005), focusing on basal mesoeucrocodylians generally and Araripesuchus in particular (Appendix B). Characters are from Clark (1994). Character 1 is modified according to Pol (2003), while characters are unmodified. Characters are from Buckley and Brochu (1999). Characters , 118 and 123 are modified from Ortega et al. (1996). Characters are modified from Gomani (1997). Characters are unmodified from Buckley et al. (2000). Character 121 is modified from Wu et al. (1997). Characters are modified from Sereno et al. (2003). Characters , 122 and are from Turner and Calvo (2005). Characters 128 and 129 are new. The novel characters included in the analysis are: 128 Proximal-most portion of fibular head straight to weakly developed posteriorly (0) or very strongly projecting forming distinct flange (1) (Figure 98); and 129 Posterior process of shaft in the posterior cervical ribs lacks (0) or possesses (1) a posterodorsally projecting spine at the junction with the tubercular process (Figures 96, 97). Results Eighteen most parsimonious trees were recovered with a length of 308. The consistency index (CI) was , CI(inf) was , and the retention index (RI) The character distribution postulates a pattern of relationships among the ingroup largely congruent with previous analyses (Buckley and Brochu 1999, Buckley et al. 2000, Pol 2003), although details within the larger clades vary slightly. A strict consensus of the 18 trees summarizes the results of the present analysis (Figure 93). The consensus tree is well resolved with only three three-taxon polytomies, however, the overall nodal support for the tree is generally weak. An Adams consensus of the same 18 trees is identical to the strict consensus and provides no information as to the contributing factors of these unresolved regions. Examination of the individual trees reveals that the three taxa responsible for the collapsed nodes are the relatively incomplete Araripesuchus wegeneri, Bernissartia and Iberosuchus. The strict consensus demonstrates that the four species of Araripesuchus form a monophyletic group, with the two South American taxa A. gomesii and A. patagonicus being more closely related to each other than to other Araripesuchus species. Other large-scale clades recovered in the analysis include a monophyletic Neosuchia, with a clade including Araripesuchus comprising its sister group. Outside of this node, a large clade of crocodyliforms including traditional notosuchian taxa and a monophyletic Sebecosuchia was recovered. In composition, this clade (notosuchians plus sebecosuchians) is similar to the Ziphosuchia clade of Ortega et al. (2000) or the Notosuchia of Sereno et al. (2001). Topologically, the Ziphosuchia clade of this analysis and that of Ortega et al. (2000) differ considerably in the placement of the four taxa shared in common. Essentially, there is a nearly complete reordering of the four taxa with Baurusuchus being the most derived and Sebecus the most basal of the sebecosuchians. The converse topology is present in Ortega et al. (2000). It is difficult to make a meaningful comparison between topologies including the notosuchian taxa because so few are in common in this and the aforementioned analyses. Ortega et al. (2000) included only Notosuchus, while Sereno et al. (2001) examined Notosuchus, Malawisuchus and Simosuchus. The relationship between these three taxa, however, was unresolved in Sereno et al. (2000).

88 New Araripesuchus from Madagascar 341 Figure 93. Phylogenetic relationships within Araripesuchus and Mesoeucrocodylia proposed in this study. Tree is a strict consensus of 18 most parsimonious trees (length ¼ 308, CI ¼ ). Paired numbers at nodes indicate bootstrap support (top) and decay index (bottom). Single numbers indicate decay index for nodes with bootstrap values less than 50.

89 342 A. H. Turner Pol and Norell (2004) have a considerably larger proportion of notosuchian taxa represented in a recent phylogenetic analysis of crocodyliforms. Again, the discrepancies in taxonomic sampling make comparison difficult. It is worth noting, however, that the Uruguaysuchus þ Simosuchus clade recovered in the present analysis was not recovered in Pol and Norell s, while Malawisuchus was found closer to Notosuchus than to Uruguaysuchus. Exploration of notosuchian and sebecosuchian relationships is not the aim of this study, therefore further discussion of these groups will not be considered. The phylogenetic position of Araripesuchus A complete list of apomorphies for one of the most parsimonious trees is provided in Appendix C. Two alternate topologies, identical to the first tree except for the placement of Araripesuchus wegeneri, were used to explore possible character support for alternate ingroup relationships within Araripesuchus. Both alternative topologies are depicted in Appendix C. The only clades discussed here are those directly pertinent to Araripesuchus relationships and the taxon s position relative to other crocodyliforms. Unnamed clade Araripesuchus1Mahajangasuchus1 Peirosauridae1 Trematochampsa Unambiguous Synapomorphy. Choanae divided by a septum (69-1), cervical vertebrae with well-developed hypapophyses (91-1), anterior margin of femur bears flange for caudofemoralis musculature (103-1; Figure 94), scapular blade very broad and greater than twice the length of the scapulocoracoid articulation (106-1; Figure 95), posterodorsally projecting spine at the junction of the tubercular process with the shaft in posterior cervical ribs (129-1; Figure 96). Ambiguous character support. Rostrum constricted at contact with premaxilla and maxilla, forming narrow slit (9-2), quadratojugal extends dorsally as a broad sheet contacting most of postorbital portion of postorbital bar (19-1), dorsal part of postorbital bar constricted, distinct from dorsal part of postorbital (29-1), dorsal osteoderms with straight anterior edge (96-0), teeth serrated (104-1). Discussion. This clade is supported by a number of derived characters, but it can be diagnosed on the basis of a very broad scapular blade that is twice the length of the scapulocoracoid articulation. In general appearance, the scapular blades of Araripesuchus and Mahajangasuchus insignis are similar (Figure 95). The anterior margin is strongly concave in contrast to the straight posterior margin. Figure 94. Systematic variation in the anterior margin of femur. A, Medial view of left femur of Mahajangasuchus insignis (UA 8654; right) and Araripesuchus tsangatsangana (FMNH PR 2300; left) showing state 1 of character 103.B, Medial view of right femur of Goniopholis (AMNH 620; left) and left femur of Protosuchus richardsoni (AMNH 3024; right) showing state 0 of character 103. Scale ¼ 1 cm. A septate choana and cervical vertebrae with welldeveloped hypapophyses are also diagnostic for this group. Within the context of Crocodyliformes, these features are not unique to the clade. A septate choana is present within goniopholids as well as Notosuchus terrestris and Iberosuchus macrodon. Welldeveloped cervical hypapophyses are also more widespread than just this clade. The trait is present in Crocodylia as well as being known in Malawisuchus mwakayasyunguti. This character may, indeed, be a more widespread mesoeucrocodylian trait, but a paucity of postcranial remains (especially within notosuchian taxa) prevents testing the full extend of the characters distribution.

90 New Araripesuchus from Madagascar 343 Figure 95. Systematic variation in scapula shape. A, Medial view of left scapula of Mahajangasuchus insignis (UA 8654; left) and Araripesuchus tsangatsangana (FMNH PR 2313; right) showing state 1 of character 106. B, Medial view of left scapula of Alligator mississippiensis (AMNH 1106) showing state 0 of character 106. Scale ¼ 1 cm. Members of this clade possess a distinct flange on the anterior margin of the femur (Figure 94). This flange corresponds to the insertion of the caudofemoralis musculature and perhaps the puboischiofemoralis internus 1. Uruguaysuchus aznarezi has a similar flange, but again due to little postcranial material, it is unclear if this is more widespread among notosuchians or mesoeucrocodylians in general. Figure 96. Systematic variation in the body of cervical ribs. A, Lateral view of right cervical rib of Mahajangasuchus insignis (UA 8654; right) and left cervical rib of Araripesuchus tsangatsangana (FMNH PR 2298; left) showing state 1 of character 129.B, Medial view of right cervical rib of Alligator mississippiensis (AMNH 1106 CA) showing state 0 of character 129. Scale ¼ 1 cm.

91 344 A. H. Turner Figure 97. Medial view of cervical ribs of Mahajangasuchus insignis (A) and Alligator mississippiensis (B) showing nature of cervical spine. Note lateral margin of concave medial surface present in both ribs (lower arrows). Upper arrows indicate presence of spine (left) and smooth margin (right). The structure in Mahajangasuchus and Araripesuchus is better described as a spine than a bifurcation given the continuity of the concave medial surface in both taxa. Scale ¼ 1 cm. Mahajangasuchus insignis and Araripesuchus possess a posterodorsally projecting spine on the shaft of the posterior cervical ribs at the junction with the tuberculum (Figure 96). The size and exact position of this spine on the rib shaft is variable in both taxa, but this variation is slight. It is uncertain if Peirosaurus, Lomasuchus, and Trematochampsa have this feature, so character is currently unambiguously optimized as synapomorphic for this larger unnamed clade. It may, however, turn out to be a putative synapomorphy for a Mahajangasuchus þ Araripesuchus clade. Buckley and Brochu (1999:158) noted that the bodies of the ribs of c4 and c5 are bifurcated in Mahajangasuchus insignis. The medial surface of the posterior process of most crocodyliforms consists of a concavity for the contact with the anterior process of the next cervical rib. This concavity is intact in Mahajangasuchus insignis with a distinct bounding rim like that seen in Alligator (Figure 97). Since this concavity is not bisected, the morphology of the rib is not well defined as being bifurcated, and the posterodorsal projecting structure is better characterized as a spine or process. Given the present homology assessment, the dorsal protuberance noted on the shaft of the c6 rib is homologized with the spines present on the preceding vertebrae. The c3 ribs are not preserved in Mahajangasuchus insignis but Araripesuchus tsangatsangana and Araripesuchus gomesii, which preserve the element, lack a spine on this cervical rib. Unnamed clade (a.k.a Araripesuchus Price 1959) Araripesuchus wegeneri 1 Araripesuchus tsangatsangana 1 Araripesuchus patagonicus 1 Araripesuchus gomesii Unambiguous synapomorphy. Frontal extends only slightly, or not at all, into the supratemporal fossa (23-1), posterior cheek teeth laterally compressed (116-1), cheek teeth constricted at base of crown (117-1), mandibular condyle of quadrate positioned ventral to occipital condyle (121-0). Ambiguous character support. Occipital condyle in posteroventral position (114-1), proximal-most portion of fibular head very strongly projecting posteriorly forming a distinct flange (128-1; Figure 98). Discussion. An Araripesuchus clade has numerous characters supporting its monophyly. Unfortunately, only one of these characters is unique to the group. Price (1959) cited frontals extending only slightly, or not at all, into the supratemporal fossa as diagnostic of Araripesuchus. This analysis recovered this traditional characteristic as a synapomorphy for Araripesuchus. This feature, however, is a much more prevalent trait, being present in Alligatorium, Goniopholis and Ziphosuchia (although it is reversed in Uruguaysuchus aznarezi and Simosuchus clarki). Likewise, laterally compressed posterior cheek teeth and cheek teeth constricted at the base of the crown are seen in other taxa. Lateral compression of cheek teeth is known in peirosaurids and is optimized as a synapomorphy for a Ziphosuchia clade, with Bretesuchus bonapartei the only exception as it retains the ancestral condition of conical teeth. Moreover, the cheek teeth of Uruguaysuchus aznarezi, Simosuchus clarki and Malawisuchus mwakayasyunguti are similar to Araripesuchus with basally constricted tooth crowns. A reversal to the primitive condition for crocodyliforms is seen in the position of the mandibular condyle of the quadrate. Crocodyliforms in the least inclusive clade containing Araripesuchus and Crocodylia have mandibular condyles that are situated level with the occipital condyle. The ancestral condition for Crocodyliformes is for the condyles to be positioned ventral to the occipital condyle. This is the condition present in Araripesuchus. The two characters ambiguously supporting this node could not be coded for A. wegeneri. Asaresult,only ACCTRAN optimized them at the Araripesuchus node. Removal of A. wegeneri from the analysis therefore results in unambiguous optimization of these characters as apomorphic for the three remaining Araripesuchus taxa. One of these characters (an occipital condyle in posteroventral position) is found in notosuchian and sebecosuchian taxa, though not in Sebecus icaeorhinus.

92 New Araripesuchus from Madagascar 345 Figure 98. Lateral views of crocodyliform fibulae showing systematic variation in fibular head. Protosuchus richardsoni (AMNH 3024; A) and Alligator mississippiensis (AMNH 1106 CA) show state 0 of character 128. Araripesuchus gomesii (AMNH 24450; C) and A. tsangatsangana (FMNH PR 2300; D) show the derived state 1 with the strongly inflected posteriorly projecting fibular head. Fibulae are scaled to the same size. Protosuchus and Araripesuchus tsangatsangana are reflected vertically to facilitate comparison. A pronounced, greatly developed posteriorly-directed fibular head is the one unique trait for Araripesuchus (Figure 98). Mahajangasuchus insignis and Malawisuchus mwakayasyunguti have enlarged fibular heads, but this is not to the extent seen in Araripesuchus nor do the fibular heads project posteriorly as strongly. Possible clade Araripesuchus wegeneri 1 Araripesuchus patagonicus 1 Araripesuchus gomesii Unambiguous synapomorphy. There are no unambiguous synapomorphies. Ambiguous character support. Jugal rod-shaped beneath infratemporal fenestra (18-1), bar between orbit and supratemporal fenestra narrow, with sculpturing on anterior part only (32-1), dentary does not extend beneath fenestra (70-1), osteoderms absent from ventral part of trunk (100-0), surface of choanal septum marked by ventral groove (126-1). Discussion. This clade is supported by no unambiguous synapomorphies. In fact, only under the ACCTRAN setting are any characters optimized at this node. Under this condition, the characters supporting this group are simply being pulled down from the A. gomesii þ A. patagonicus node. None of the five characters thereby providing ambiguous support for this clade are even known for A. wegeneri. Given the current character distributions and until further material is recovered and described

93 346 A. H. Turner Figure 99. for Araripesuchus wegeneri, I view this possible clade as unlikely. Possible clade Araripesuchus wegeneri 1 Araripesuchus tsangatsangana Restoration of Araripesuchus tsangatsangana. Original illustration by Carolyn McKee-Freese. Unambiguous synapomorphy. There are no unambiguous synapomorphies. Ambiguous character support. Osteoderms absent from ventral part of trunk (100-0), snout relatively broad and shorter than the remainder of the skull (112-1), occipital condyle in posteroventral position (114-1), proximal-most portion of fibular head very strongly projecting posteriorly forming a distinct flange (128-1). Ambiguous character support. Premaxilla forms little, if any, of internarial bar (4-1), nasal does not contact lacrimal (11-1), retroarticular process posteriorly projecting from ventral part of mandible and attenuating (71-6). Discussion. This clade is supported by no unambiguous synapomorphies. Similar to the previous possible clade, it is only under the ACCTRAN setting that any characters optimize at this node. Under this condition, the characters supporting this group are again simply being pulled down from the A. gomesii þ A. patagonicus node. None of the three characters providing ambiguous support for this clade are known for A. wegeneri. Given the current character distributions I view this possible clade as unlikely. Preferred clade Araripesuchus tsangatsangana 1 Araripesuchus patagonicus 1 Araripesuchus gomesii Unambiguous synapomorphy. Teeth without carinae, or with smooth carinae (104-0). Discussion. When Araripesuchus wegeneri is included in the analysis, character support for this group is weak. Nonetheless, this is the favored topology for this analysis because character support is stronger than for the alternate topology discussed above. In the context of the position of these three taxa in a clade with Mahajangasuchus insignis, Peirosauridae, and Trematochampsa, their shared loss of teeth carinae is considered an unambiguous trait diagnosing the group. A. wegeneri in this situation retains the primitive condition of serrated carinae that is present in the closest relative of the Araripesuchus clade. In fact, serrated carinae are even more widespread among crocodyliforms, with some notosuchians and nearly all sebecosuchians possessing the trait. The absence of osteoderms from the ventral part of the trunk may also diagnose this group, however, the trait is not known in Araripesuchus tsangatsangana. In addition, DELTRAN optimizes a relatively broad and short snout as a synapomorphy of this clade. Two characters discussed earlier as possible synapomorphies for Araripesuchus proper may diagnose this more inclusive clade depending on how the

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