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University of Iowa Iowa Research Online Theses and Dissertations Spring 2016 A reassessment of the late Eocene - early Oligocene crocodylids Crocodylus megarhinus Andrews 1905 and Crocodylus articeps Andrews 1905 from the Fayúm Province, Egypt Amanda Jane Adams University of Iowa Copyright 2016 Amanda Jane Adams This thesis is available at Iowa Research Online: http://ir.uiowa.edu/etd/3033 Recommended Citation Adams, Amanda Jane. "A reassessment of the late Eocene - early Oligocene crocodylids Crocodylus megarhinus Andrews 1905 and Crocodylus articeps Andrews 1905 from the Fayúm Province, Egypt." MS (Master of Science) thesis, University of Iowa, 2016. http://ir.uiowa.edu/etd/3033. Follow this and additional works at: http://ir.uiowa.edu/etd Part of the Geology Commons

A REASSESSMENT OF THE LATE EOCENE EARLY OLIGOCENE CROCODYLIDS CROCODYLUS MEGARHINUS ANDREWS 1905 AND CROCODYLUS ARTICEPS ANDREWS 1905 FROM THE FAYÚM PROVINCE, EGYPT by Amanda Jane Adams A thesis submitted in partial fulfillment of the requirements for the Master of Science degree in Geoscience in the Graduate College of The University of Iowa May 2016 Thesis Supervisor: Professor Christopher A. Brochu

Copyright by AMANDA JANE ADAMS 2016 All Rights Reserved

Graduate College The University of Iowa Iowa City, Iowa CERTIFICATE OF APPROVAL This is to certify that the Master's thesis of MASTER'S THESIS Amanda Jane Adams has been approved by the Examining Committee for the thesis requirement for the Master of Science degree in Geoscience at the May 2016 graduation. Thesis Committee: Christopher A. Brochu, Thesis Supervisor Jonathan Adrain Justin Sipla

ACKNOWLEDGEMENTS For access to specimens, I would like to thank the The Natural History Museum, London, England, the American Museum of Natural History, New York, New York, and the Peabody Museum of Natural History, Yale University, New Haven, Connecticut. I would also like to thank Dr. Christopher Brochu for access to his collection of specimen photographs. I would like to thank my advisory committee, Dr. Christopher Brochu, Dr. Jonathan Adrain, and Dr. Justin Sipla, along with the office staff and my other professors at the University of Iowa. Finally, I would like to thank my family and friends who have encouraged me throughout my education and research. ii

ABSTRACT The Fayúm Province of Egypt covers an almost continuous time span from the middle Eocene through the early Oligocene and has produced a number of vertebrate fossils important to evolutionary history. This area includes early crocodylids inaccurately assigned to crown-group Crocodylus, which has been shown through molecular and morphological phylogenetic analyses to have diverged during the Miocene. We reviewed two taxa from the early Oligocene Gebel Qatrani Formation, Crocodylus megarhinus Andrews 1905 and Crocodylus articeps Andrews 1905, which had previously been synonymized, with C. articeps thought to be based on a juvenile specimen of C. megarhinus. Crocodylus megarhinus outwardly resembles most living species of Crocodylus, however it is a basal crocodylid lacking diagnostic features for the crown genus. The holotype of C. articeps is now lost, but based on a cast and published images of the original material, it was a slender-snouted form that can be distinguished from smaller specimens of C. megarhinus. Although not synonymous with C. megarhinus, C. articeps cannot be diagnosed or scored for existing character matrices sufficiently to allow precise phylogenetic placement. Previous analyses of C. megarhinus included information from C. articeps; recoding C. megarhinus based only on material referable to that species does not change its phylogenetic position, but it forces a reconsideration of the polarity of character states in clades leading to the origin of crown-genus Crocodylus which, in turn, may inform efforts to resolve the relationships among living crocodylid lineages. Based on its confirmed phylogenetic position as a basal crocodylid, C. megarhinus provides insight iii

into the ancestral conditions of all crocodylids and supports an African origin for Crocodylidae. iv

PUBLIC ABSTRACT The Fayúm Province of Egypt occupies a depression just west of the Nile Valley. Heavily explored throughout the late 1800s and early 1900s the area is known for the variety of well-preserved fossils covering an almost continuous time span from the Middle Eocene through Early Oligocene. The area is best known for the discovery of early whale relatives and early primates and as such a majority of the work focuses on them. Several crocodylians have been found in these deposits, yet very little work has been done to revisit these specimens. In this study, specimens of the Early Oligocene Crocodylus megarhinus Andrews 1905 and Crocodylus articeps Andrews 1905 are reexamined in order to determine validity of each species and provide insight into the relationships among early crocodylids. Historically the name Crocodylus Laurenti 1768 was applied to any fossil crocodylian that fit the general form of a crocodile. Molecular and morphological analysis have placed the divergence of this group of animals during the Miocene. Many species referred to Crocodylus early on likely do not belong there. It is necessary to revisit many of the earlier crocodylians in order to establish where they belong and clarify the phylogenetic relationships within Crocodylia. A phylogenetic analysis confirms the placement of C. megarhinus outside the crown-group Crocodylus and instead places it as a basal member of family Crocodylidae. This provides support to establish a new genus for C. megarhinus, while C. articeps is designated nomen dubium due to the loss of the original specimen. v

TABLE OF CONTENTS LIST OF FIGURES... vii CHAPTER I... 1 INTRODUCTION... 1 Statement of Purpose... 6 Geologic Setting... 6 Previous Work... 9 CHAPTER II... 11 MATERIALS AND METHODS... 11 Methods... 11 Institutional Abbreviations... 12 List of Reference Specimens... 12 CHAPTER III... 13 DESCRIPTION OF CROCODYLUS MEGARHINUS... 13 Principle Cranial Openings... 13 Cranial Bones... 21 Bones of the Lower Jaw... 31 CROCODYLUS ARTICEPS... 44 CHAPTER IV... 47 RESULTS... 47 CHAPTER V... 50 DISCUSSION... 50 Validity of Crocodylus articeps... 64 CONCLUSION... 68 APPENDIX A. TABLE OF REFERENCE SPECIMENS... 69 APPENDIX B. LIST OF CHARACTERS USED IN DESCRIPTIVE MATRIX... 72 APPENDIX C. MATRIX OF CHARACTERS IN PHYLOGENETIC ANALYSIS... 85 APPENDIX D. CHARACTER COMPARISON... 93 APPENDIX E. CHARACTER-STATE OPTIMIZATION... 94 Apomorphy List... 96 REFERENCES... 100 vi

LIST OF FIGURES Figure 1: Crocodylus articeps, cast of holotype, NHMUK R. 3322...4 Figure 2: Crocodylus megarhinus, holotype, NHMUK R. 3327...5 Figure 3: Dorsal view of Crocodylus megarhinus...14 Figure 4: Dorsal view of Crocodylus megarhinus...16 Figure 5: Dorsal view of Crocodylus megarhinus...18 Figure 6: Occipital view of Crocodylus megarhinus...28 Figure 7: Palatal view of Crocodylus megarhinus...32 Figure 8: Palatal view of Crocodylus megarhinus...34 Figure 9: Palatal view of Crocodylus megarhinus...36 Figure 10: Lateral view of Crocodylus megarhinus...40 Figure 11: Dorsal view of Crocodylus megarhinus...42 Figure 12: Dorsal view of Crocodylus articeps...45 Figure 13: Strict consensus of 60 equally optimal trees...48 Figure 14: Dorsal, lateral, and palatal view of Crocodylus articeps skull...51 Figure 15: Adams consensus of 60 equally optimal trees...56 Figure 16. Simplified optimized tree based on ACCTRAN and DELTRAN optimizations...60 vii

CHAPTER I INTRODUCTION The Fayúm Province of Egypt, located west of the Nile Valley, is a depression in the desert spotted with bodies of water varying in size and salinity. A large, brackish lake called Birket-el-Qarun occupies the lowest part of the depression. It is along the northern margin of this lake where Cenozoic vertebrate fossils were first collected by G. Schweinfurth in 1879. Exploration of this area for vertebrate remains was sporadic until a survey by H. J. L. Beadnell was conducted in 1898. Through his efforts a large quantity of vertebrate remains were collected from this area in the early 1900 s. Spanning the Middle through Upper Eocene and Early Oligocene, this sequence of rocks has produced fossil mammals, selachians, teleosts, birds, and reptiles (Andrews, 1906; Gingerich, 1993). Several crocodylians have been found in these deposits, yet very little work has been done to revisit these specimens. Accurate descriptions of their morphology are required in the ongoing process to understand crocodylian phylogenetics (Brochu and Gingerich, 2000). Historically the name Crocodylus Laurenti 1768 was applied to any fossil crocodylian that resembled most modern crododiles. Molecular analysis of living members of Crocodylus place the divergence of this clade during the Miocene (Densmore, 1983; Densmore and Owen, 1989; Hass, 1992; Oaks, 2011). This is consistent with phylogenetic analyses of morphological data including fossils (e.g. Brochu, 2000). Many species referred to Crocodylus early on, including some from the Eocene and Oligocene of the Fayúm region, likely do not belong there. It is necessary to 1

revisit many of the earlier crocodylians in order to establish where they belong and clarify the phylogenetic relationships within Crocodylia. The subjects of this project are the remains of two crocodylians from the Upper Eocene-Early Oligocene of the Fayúm Province of Egypt. Crocodylus articeps Andrews 1905 (Figure 1) was described as a narrow-snouted species and Crocodylus megarhinus Andrews 1905 (Figure 2) had a shorter, broader snout. Both were briefly described by C. W. Andrews in 1905. He later published a more detailed description and figured the specimens in the Catalogue of the Tertiary Vertebrata of the Fayúm (1906). Another specimen of C. megarhinus, discovered near Birket-el-Qarun, was collected in 1907 and described by Charles C. Mook in 1927. This specimen is far more complete when compared to the type specimen but has undergone mild deformation and was prepared for collections with a coating of lacquer, which makes identification of cranial sutures difficult. These are the most complete published descriptions of either species. There is also an unpublished juvenile specimen of C. megarhinus, collected in the 1960 s, that will prove useful in a new description. Brochu (2000) regarded C. megarhinus and C. articeps as synonymous, with C. megarhinus representing a more mature individual. Within modern crocodylids and their Neogene fossil relatives we see multiple instances of long-snouted, blunt-snouted, and more generalized forms evolving independently throughout the lineage (Brochu, 2001; McAliley et al, 2006; Brochu, 2007). As a basal member of Crocodylidae, C. megarhinus provides insight into ancestral conditions of all crocodylids and a better understanding of how character states have changed throughout the lineage. It might also help constrain divergence times within Crocodylidae in general and of late Cenozoic African lineages in particular. 2

Historically it was believed that Crocodylus originated in Africa during the Cretaceous (Lydekker, 1886; Mook, 1927, 1933; Sill, 1968; Buffetaut, 1984). With the application of molecular phylogenetics we now place the divergence times between Crocodylus and its closest relatives in the Miocene (Brochu, 2000; Oaks, 2011). There is broad agreement that the two recently-split (Hekkala et al. 2011) living African species Crocodylus niloticus Laurenti 1768 and Crocodylus suchus Geoffroy 1807 are closely related to a clade of Neotropical species and that the closest living relatives of Crocodylus are the African dwarf crocodiles (Osteolaemus Cope 1861) and African sharp-nosed crocodiles (Mecistops Gray 1844; Brochu, 2000; Meganathan et al, 2011; Meredith et al, 2011; Oaks, 2011). But whether the Australasian species of Crocodylus form a clade (Brochu, 2000) or a series of sequential outgroups to the African-Neogene group (Meganathan et al, 2011; Meredith et al, 2011; Oaks, 2011) is debated. It is also unclear whether Mecistops is more closely related to Crocodylus or to Osteolaemus (McAliley et al., 2006). As a result, the origins of living African crocodiles are unresolved. Resolution may come from a better understanding of basal crocodylid phylogeny, which in turn will require detailed information from the morphology of fossils. 3

Figure 1: Crocodylus articeps, cast of holotype, NHMUK R. 3322 Scale = 10 cm 4

Figure 2: Crocodylus megarhinus, holotype NHMUK R. 3327 Scale = 10 cm 5

Statement of Purpose The purpose of this study is to compile a detailed description of the cranial anatomy of Crocodylus megarhinus and establish if it belongs within a new or preexisting genus based on an updated phylogenetic analysis. It will also test the conclusions drawn by Brochu (2000) that C. articeps and C. megarhinus are based on specimens of the same species. The status of each is reassessed. Geologic Setting The Fayúm province of Egypt is a roughly circular depression located south of Cairo and separated from the Nile by a narrow strip of desert. A brackish body of water covering approximately 202 square kilometers called Birket-el-Qarun, the third largest lake in Egypt, now occupies the northwestern region of the depression. The only source of incoming water enters the depression through the Bahr-el-Yusef canal. During the Cenozoic present-day Egypt occupied part of the northern edge of the African continent. It was bordered in the northwest by the Tethys Sea, which ran across northern Egypt in a roughly WSW-ENE direction. The rock records show deeper marine deposits overlain by shallower marine to terrestrial deposits. This is interpreted as regression of sea level occurring throughout the Eocene and Oligocene, with continental deposits prograding north and west (Gingerich, 1993). There are four main deposits of Eocene age known to be fossiliferous. The Gehannam Formation is Bartonian to early Priabonian in age and consists of calcium carbonate rich mudstones and argillaceous limestones shifting to claystones and siltstones interbedded with sandstones higher up. Various foraminifera, mollusks, sharks, fish, and 6

marine mammals are found in this deposit. The Birket Qaroun Formation is early Priabonian and is composed of fine, bioturbated sandstone and calcareous silty sandstones. This formation is known for its well preserved marine mammals, sharks, crocodiles, turtles, fish and mollusks. There are also terrestrial fossils including snake and elephant. The Garet el-naqb Formation is Priabonian and consists of a dark gray claystone intermittently cut by gypsum veins. The fossils are far fewer and consist of foraminifera, mollusks, and fish. The final Eocene deposit is the Qasr el-sagha Formation which consists of shales inserted with layers of limestones and sandstones. The fossils of this deposit include mollusks, foraminifera, marine mammals, fish, turtle, and a few terrestrial mammals (Gameil et al., 2016). The type specimens of both C. megarhinus and C. articeps are recorded as being from the fluvio-marine beds located north of Birket-el-Qarun (Andrews 1906). The fluvio-marine series (Jebel el Qatrani Series) described by Beadnell (1905) is a series of variegated sands and sandstones cut by alternating beds of clay and clayey marl, a sequence unique to those that precede it. He also notes a black band of basalt that caps many outcrops of the series, which is further overlain by more sediment similar in composition to the fluvio-marine beds. This particular series of rock has produced large quantities of silicified wood together with remains from a variety of land animals including mammals, birds, reptiles, and fish. While many specimens were well preserved Beadnell noted that many were new and therefore were little help in determining the age of the beds. It is the preservation of a variety of mollusks that were identified for Beadnell by Blanckenhorn, based off of his own work published in 1901, which allowed for a determination in age. Blanckenhorn asserts that the upper portion of the fluvio- 7

marine beds were to be regarded as Lower Oligocene while the lower portion was Upper Eocene, the band of basalt acting as a tentative boundary between the two. Therefore both of the holotypes are recorded as being Upper Eocene in age. Various works have since tried to assign what is now called the Gebel Qatrani Formation an age. This has varied from late Eocene (Van Couvering and Harris, 1991; Rasmussen et al., 1992) to completely Oligocene (Blanckenhorn, 1903; Stromer, 1907). Work by Gingerich (1993) has since reassessed the fluvio-marine beds described by Beadnell. Based on a comprehensive analysis of the sequence stratigraphy throughout northern Egypt Gingerich confirms the presence of an unconformity between the Qasr el- Sagha and Gebel Qatrani Formations previously noted from isolated localities by various authors (Beadnell, 1905; Barron, 1907; Bown and Kraus, 1988; Rasmussen et al., 1992). Gingerich estimates erosion of a minimum of 76 m of the Eocene Qasr el-sagha Formation occurred before the deposition of the Gebel Qatrani Formation. This amount of erosion was likely the result of rapid sea level fall, of which there are three occurrences from the middle to late Eocene and Oligocene. With the additional use of biostratigraphy and radiometric dates obtained from basalts, Gingerich was able to identify the latest sea level drop as the only possible candidate. It occurred at the Priabonian-Rupelian boundary, marking the Gebel Qatrani as Oligocene in age (Gingerich, 1993). These new conclusions thus suggest that the holotypes of C. megarhinus and C. articeps are from the early Oligocene. The rest of the specimens referred to either species have been assigned either Upper Eocene or early Oligocene. A few were recorded as having been collected in the Gebel Qatrani Formation while others are merely given a 8

vague direction relative to Birket-el-Qarun. Without more precise maps of the collection sites it is hard to access the temporal range of these species. Previous Work The holotype specimens of C. megarhinus and C. articeps were collected in 1903 during expeditions into the Fayúm depression led by Mr. H. J. L. Beadnell (Andrews 1905, 1906). The holotype of C. megarhinus (R. 3327) was presented to The Natural History Museum, London by Mr. William E. de Winton. The holotype of C. articeps (C. 10036) was deposited in the Egyptian Geological Museum, and a cast (R. 3322) was made for The Natural History Museum (Andrews, 1906). Some initial notes were published on both specimens in Andrews (1905). The full descriptions and figures were later published in Andrews (1906). Andrews (1905, 1906) described C. megarhinus as a large, broad-snouted crocodile. While comparable in size to Crocodylus porosus Schneider 1801, Crocodylus paludosus, and Crocodylus niloticus Laurenti 1768, Andrews noted the elongation of the premaxillary region and the extended mandibular symphysis as distinguishing characteristics for C. megarhinus (Andrews, 1906). A far more complete specimen (AMNH FARM 5061) collected in 1907 by the American Museum of Natural History (AMNH) was described by Mook (1927). Mook affirmed the similarity to C. niloticus but further described the greater proportional snout length to total skull length and the proportionally small skull table found in C. megarhinus when compared to C. niloticus. He further described an unassociated mandible (AMNH FARB 5095) collected in 1909 he attributed to C. megarhinus. With this specimen he further distinguished C. megarhinus from C. porosus through the length of the dental series. Based on the 9

similarities with C. niloticus, Mook proposed C. megarhinus as a direct ancestor of C. niloticus. Other authors have been more cautious in this (e.g., Müller, 1927; Tchernov, 1986; Leakey et al., 1996). Leakey et al. (1996) suggested it is merely a functional and ecological precursor to C. niloticus. Yet another description was published by Müller (1927). Further research within Crocodylidae has shown C. megarhinus to be outside the crown-genus Crocodylus (Brochu, 2000). Andrews (1905, 1906) described C. articeps as a long, narrow-snouted crocodile. He compared this specimen to Mecistops cataphractus (Cuvier 1824) and Crocodylus intermedius Graves 1819 in that they all share similar snout dimensions, but noted that C. articeps has much longer nasals and an expansion of the premaxillary region. He also noted Megadontosuchus arduini (Zigno 1880) as potentially the most similar, but differing in that C. articeps has a smaller expansion of the premaxillary region, a narrower interorbital bar, and less rounded orbits. While several crocodylians have been found in the Fayúm, compared to the mammalian fossil record very little work has been done to revisit them. In Brochu (2000), the author regarded C. megarhinus and C. articeps as synonymous, with C. megarhinus representing a more mature individual. Reasons for this designation are not expressly laid out. Subsequent works have accepted this assertion and C. articeps is no longer seen in the literature. 10

CHAPTER II MATERIALS AND METHODS Methods Specimens of Crocodylus megarhinus, Crocodylus articeps, and other relevant taxa from the Fayúm of Egypt were surveyed in the American Museum of Natural History (New York City, NY), the Yale Peabody Museum of Natural History (New Haven, CT), and Natural History Museum (London, England), which houses the holotype specimen of C. megarhinus and a cast of the holotype of C. articeps. The holotype of C. articeps was housed at the Egyptian Geological Museum, but it was lost or destroyed during a recent museum relocation (M. Gawad, personal communication). All information about C. articeps was gathered from the cast of the holotype (which preserves some sutural contacts) and the original description by C. W. Andrews (1905, 1906). Each specimen was photographed and drawn. For every specimen I made note of the completeness, quality of preservation, and any evidence of deformation. Sutures and other distinct features were identified as preserved. Well preserved specimens were coded according to the character matrix from Brochu (2012). This consists of 189 binary or multistate morphological characters. I ran a maximum-parsimony analysis of this matrix including all current taxa within Crocodyloidea. Leidyosuchus canadensis Lambe 1907, the most basal alligatoroid (Brochu 1997), was used as an outgroup to establish polarity and root the trees. The phylogenetic analysis was performed through TNT (Version 1.1; Goloboff and Nixon, 2000). The analysis used a traditional search which features randomized 11

stepwise addition and branchswapping. In Winclada (Version 0.9.9; Nixon, 1999) I made a strict consensus. Bootstrap scores and Bremer support scores were obtained in TNT using the GC metric option with 10,000 pseudoreplicates and the Trees-Bremer Supports analysis respectively. Using trees obtained from the TNT analysis an Adams Consensus was created in PAUP (Version 4.0b10; Swofford, 2003). Institutional Abbreviations All specimens were examined at the institution housing them. AMNH: American Museum of Natural History (New York City, NY) NHMUK: The Natural History Museum (London, England) GMCE: Geological Museum of Cairo (Cairo, Egypt) YPM: Peabody Museum of Natural History, Yale University (New Haven, CT) List of Reference Specimens Crocodylus articeps: NHMUK R. 3322 (cast of holotype), NHMUK R. 3323 Crocodylus megarhinus: NHMUK R. 3327 (holotype), NHMUK R. 3328, FARB AMNH 5061, FARB ANMH 5062, FARB AMNH 5064, FARB AMNH 5095, YPM 9012, YPM VP-058532 Above is a list of specimens used in coding for phylogenetic analysis. A full list of reference specimens is available in Appendix A. 12

CHAPTER III DESCRIPTION OF CROCODYLUS MEGARHINUS The following description is the summary of multiple specimens, including the type (see List of Reference Specimens), to produce a description that is as complete and accurate as possible. The external surface of all specimens is covered in shallow, irregular pits. The snout shape of C. megarhinus is that of a generalized crocodylian. The snout is compressed dorsoventrally and tapers gradually towards the anterior (Brochu, 2001). Dentary teeth occlude in line with the maxillary toothrow, and dentary tooth four occludes in a notch between the premaxilla and maxilla. The teeth are circular in cross section with smooth carinae. Principle Cranial Openings External Naris: The external naris is large and projects dorsally. It is longer than it is wide. The outline is pinched towards the interior at both the anterior and posterior edges. The lateral edges are gently curved and converge slightly towards the posterior. The overall shape resembles an apple. For the purposes of the coding matrix it is considered circular. A bony bar created by the anterior process of the nasals bisects the nares (Figures 3, 4, 5). Choana: The choana is average size, located posteromedially, and is oriented posteroventrally. It is completely surrounded by the pterygoids. The only preserved example of the choana is somewhat eroded, but does not appear to be notched along the posterior rim nor is it septate. The pterygoid surface is pushed inward anterolateral to the choanal aperture (Figure 8). 13

Figure 3: Dorsal view of Crocodylus megarhinus. f, frontal; j, jugal; l, lacrimal; m, maxilla; n, nasal; pa, parietal; pf, prefrontal; pm, premaxilla; po, postorbital; q, quadrate; qj, quadratojugal; so, supraoccipital; sq, squamosal. Dashed lines indicate uncertainty is suture placement. YPM VP-058532, Scale = 10 cm 14

15

Figure 4: Dorsal view of Crocodylus megarhinus. f, frontal; j, jugal; l, lacrimal; m, maxilla; n, nasal; pa, parietal; pf, prefrontal; pm, premaxilla; po, postorbital; q, quadrate; qj, quadratojugal; so, supraoccipital; sq, squamosal. Dashed lines indicate uncertainty is suture placement. Areas filled in with lines indicate plaster or epoxy repair. FARB AMNH 5061, Scale = 10 cm 16

17

Figure 5: Dorsal view of Crocodylus megarhinus. f, frontal; l, lacrimal; m, maxilla; n, nasal; pf, prefrontal; pm, premaxilla. Dashed lines indicate uncertainty is suture placement. Areas filled in with lines indicate plaster or epoxy repair. NHMUK R. 3327, Scale = 10 cm 18

19

Supratemporal Fenestrae: The fenestrae on the skull table are subcircular, converging to a slight point anteriorly. In the adult specimen they make up just under half the total width of the skull table at its widest point (Figure 4). The borders are comprised of the postorbitals, parietal, and squamosals. Infratemporal Fenestrae: The infratemporal fenestrae are medium in size, being slightly larger than the supratemporal fenestrae, and are elongate anteroposteriorly. They project dorsally. The borders are comprised of the postorbital, jugal, quadratojugal, and quadrate. The quadratojugal spine is prominent in the juvenile specimen (Figure 3) but absent in the adult, however the posterior rims of the infratemporal fenestra in the adult specimen show evidence of damage and reconstruction in epoxy (Figure 4). Orbits: The orbits are large and ovate, being compressed mediolaterally. The lateral edges are straight. A gentle, continuous curve begins at the posterolateral corner and continues along the medial edge. Each orbit converges to a rounded point anteriorly. The borders are comprised of the lacrimals, prefrontals, frontal, postorbitals, and jugals. The orbits face directly upward and the margins are flush with the skull surface in the adult specimen (Figures 3, 4). Recessa Otica Externa: The otic aperture is set deep and ventral to the overhang created by the squamosal s lateral edge. The posterior margin of the otic aperture is bowed. Posttemporal Fenestrae: The posttemporal fenestrae are reduced to slits located off the posterior edge of the skull table. The borders are comprised of the supraoccipital, parietal, and the squamosals (Figure 6). 20

Incisive Foramen: The incisive foramen is present on the premaxillary plate posterior to the second premaxillary alveoli. It is small, less than half the greatest width of the combined premaxillae. The opening converges to a rounded point anteriorly. The lateral margins are gently curved and the foramen increases in width towards the posterior. The posterior margin is separated into three lobes. The lateral two are short and rounded, while the medial lobe is narrow and pointed (Figures 3, 4). Suborbital Fenestrae: The suborbital fenestrae are large, at its greatest length it exceeds twice the greatest width. The borders are comprised of maxillae, palatines, pterygoids, and ectopterygoids. The anterior-most edge is on level with posterior margin of maxillary alveoli 8. The lateral margins are nearly straight. The posterior margin turns inward at an approximately 45º angle. At the posterior most edge the suborbital fenestra is compressed between two lobes of the pterygoid, forming a short, narrow bump within the margin of the suborbital fenestra. The opening widens again along the medial margin, curving towards the exterior. The fenestra margins converge anteriorly to form a rounded point (Figure 8). External Mandibular Fenestrae: The external mandibular fenestrae are moderate in size. The borders are comprised of the dentaries, surangulars, and angulars (Figure 10). Cranial Bones Premaxillae: The premaxillae are short, with processes extending posteriorly no further than the third maxillary alveolus. Posterior to the external naris they are separated by the nasals. They narrow gradually to form an acute point between the nasals and maxillae. The external naris is flush with the premaxillary surface, and the surface lateral to the 21

naris is smooth (Figures 3, 4, 5). Each premaxilla contains five alveoli, the fourth of which is the largest. There are distinct gaps between alveoli 1-2 and 3-4. Small foramen are present sporadically along the medial edge of the alveoli. In ventral view the premaxillae terminate at the level of the second maxillary alveoli as a gentle convex curve oriented posteriorly (Figures 7, 8). Maxillae: The maxillae flare out laterally behind the premaxillae, narrow briefly posterior to the fifth alveolus, then expand gradually posteriorly. Each maxilla contains thirteen circular alveoli. The largest alveoli are four and five, which are the same size. There are large gaps formed between maxillary alveoli 5-6, 6-7, and 7-8. Posteriorly the maxillary tooth row is bordered by the anterior process of the ectopterygoid. The maxillary foramen for the palatine ramus of cranial nerve five is small. In palatal view the maxillae form straight sutures with the premaxillae, intersecting in a shallow V at the level of the second maxillary alveoli. Posteriorly they form a rounded point with the palatines, convex anteriorly. Laterally the sutures are more irregular. The palatinemaxilla suture intersects with the suborbital fenestrae at the level of the ninth maxillary alveoli (Figures 7, 8). In dorsal view the suture with the nasals forms a gentle medial curve. The maxilla shares irregular sutures posteriorly with the lacrimal and jugal. There is a small area of raised surface located approximately dorsal to the fifth maxillary alveolus (Figures 3, 4). Nasals: Anteriorly the nasals bisect the posterior margin of the external naris. At the approximate level of the anterior most edge of the maxillae the nasals begin to widen gradually, reaching their greatest width at the level of the third maxillary alveolus. The suture with the maxillae form very shallow curves concave outwards. At maxillary 22

alveoli eight the maxillary contact is replaced by a straight suture with the lacrimals. At the ninth alveoli the lacrimal border is replaced by the prefrontals. At this point the nasals begin to narrow gradually. The nasals terminate posteriorly at approximately the level of the twelfth maxillary alveoli. The posterior ends form acute points separated by the anterior process of the frontal, which narrows rapidly. The nasals a rejoined medially at the level of the anterior margin of the tenth alveoli (Figures 3, 4). Lacrimals: The lacrimals anteriomedial margins form a broad contact with the nasals. The lateral margin with first the maxilla and then the jugal forms a gentle, continuous curve concave inward. The maxilla-lacrimal suture is irregular. The posterior margin forms the anterior apex of the orbit. The lacrimal-prefrontal suture intersects the orbit posterior to its apex, and forms a gentle curve concave outward briefly before straightening out. At it s greatest length the lacrimal is approximately the same length as the prefrontal. There is a small ridge on the surface of the lacrimals anterior to the orbit (Figures 3, 4). Prefrontals: The prefrontals form an acute point anteriorly between the nasals and lacrimals and gradually widen posteriorly. The medial prefrontal-frontal suture is straight, but curves sharply posteriorly to intersect with the orbit (Figures 3, 4). Jugals: Anteriorly the jugals gently slope laterally towards the maxilla. The jugal forms an acute point between the maxilla and lacrimal. The jugal-lacrimal suture is irregular and intersects the orbit posterior to its anterior margin. The suture then turns anteriorly forming a small spur of jugal visible in dorsal view. Posterior to the maxilla the jugal becomes oriented near-vertical. There is a slight expansion of the jugal into the orbit anterior to the postorbital bar. Anterior to the posterior margin of the infratemporal 23

fenestra the jugal forms a concave posterior suture with the quadratojugal. The jugal narrows gradually towards the posterior, terminating in a narrow point just anterior to the end of the quadratojugal (Figures 3, 4). Of note is the deep sulcus found on the ventral margin of the jugal. While the presence of a sulcus is characteristic of many crocodiles, the depth of this sulcus is unique. The medial jugal foramen was not found during initial observation. This will require revisiting but it is likely that the foramen is large. The ventral margin of the postorbital bar is inset from the lateral jugal surface. Frontal: The frontal forms an acute point anteriorly, dividing the nasals posteriorly. It widens posteriorly, reaching a constant width at the level of the posterior-most tips of the nasals. The prefrontal-frontal suture is straight temporarily before curving sharply to intersect with the orbit. The frontal forms the posteromedial margin of the orbit. Posteriorly the margin is comprised of the parietal and laterally by the postorbitals. The frontal-parietal suture is concave anteriorly. The frontal does not participate in the supratemporal fenestrae (Figures 3, 4). Postorbitals: The postorbitals form the posterior margin of the orbits and the anteriomedial margin of the infratemporal fenestrae. They create a rounded-off square shape for the anterior edge of the skull table. The margin of the infratemporal fenestrae created by the postorbital creates an anterior point in the fenestra, with straight margins on either side. A ventral process, inset from the anterolateral edge of the skull table, descends to connect with the jugal forming the slender postorbital bar. Medially the postorbital forms sutures with the frontal and parietal, excluding the frontal from connecting with the supratemporal fenestrae (Figures 3, 4). The postorbital bar process is 24

not prominent. The postorbital-squamosal suture is oriented ventrally ventral to the skull table. Quadratojugals: The quadratojugals are bordered laterally by the jugals forming a concave posterior suture starting at the posterior angle of the infratemporal fenestra. It is medially bordered by the quadrates forming a concavoconvex suture. The quadratojugals extend to the posterior margin of the quadrates. Anteriorly they are narrow and expand gradually posteriorly. Along the dorsal surface a narrow ridge of bone is formed running from the posterolateral corner of the infratemporal fenestra, diagonally across the quadratojugal and terminating at the posterior corner of the quadratojugal. The smaller specimen (YPM VP-058532) exhibits wide quadratojugal spines intersecting the posterior margin of the infratemporal fenestra (Figures 3, 4). In palatal view the quadratojugal narrows rapidly posteriorly before terminating just anterior to the posteriormost edge of the quadrate. The sutures with both the jugal and quadrate are much smoother than in dorsal view and mostly straight (Figure 7). Quadrates: In dorsal view the quadrate forms a concavoconvex suture with the quadratojugal. The quadrate participates in the medial margin of the infratemporal fenestra. Anteromedially it is overlain by the paraoccipital process (Figures 3, 4). The quadrate-squamosal suture is straight and extends dorsally along the posterior margin of the otic aperture. They are oriented posteroventrally posterior to the paraoccipital process. The medial hemicondyle is expanded. The quadrate foramen aerum is small and located on the mediodorsal angle of the quadrate. In palatal view the quadrate shares a smooth, mostly straight lateral suture with the quadratojugal. The posterior mandibular adductor muscle scar is formed by modest crests of bone (Figure 7). 25

Parietal: Anteriorly the parietal forms an anteriorly concave suture with the frontal. Anterolaterally it forms sutures with the postorbitals, preventing the frontal from interacting with the supratemporal fenestrae. The parietal bone is raised along the curved margins of the supratemporal fenestrae, forming a shallow recess between them. Posterior to the supratemporal fenestrae there is a deeper recess within the parietal with a narrow ridge of bone bisecting it in the anterior-posterior direction. The parietalsquamosal suture intersects the posterior margin of the supratemporal fenestra, oriented posteromedially. The suture turns sharply and becomes oriented posteriorly, gradually increasing the width of the parietal. The parietal s posterior margin intersects the edge of the skull table, but is split by a dorsal exposure of the supraoccipital (Figures 3, 4). Squamosals: The squamosals gently curve laterally out, broadening the posterior half of the skull table. The posterior margin of the supratemporal fenestrae is created by the squamosal and bordered laterally by the squamosal-postorbital suture and medially by the squamosal-parietal suture. The parietal-squamosal suture is oriented posteromedially initially but turns sharply and becomes oriented posteriorly, gradually constricting the medial squamosal margin. In dorsal view the posterior process of the squamosal on the skull table is slightly raised (Figures 3, 4). In occipital view the squamosal participates in the lateral margin of the posttemporal fenestra. The squamosal-exoccipital suture is oriented lateroventrally, with the squamosal terminating as a slender process capping the exoccipital (Figure 6). Basioccipital: The basioccipital forms the ventral, half-circle margin of the foramen magnum. It expands posteriorly to form the occipital condyle, a protrusion that gradually narrows as it moves posteriorly terminating in a rounded posteroventrally facing ball. 26

Ventral to the occipital condyle, the basioccipital flares laterally. The ventral process has short, rounded ridges on both lateral margins and one central ridge called tubera. The basioccipital is rounded off ventrally, and forms the posterior walls of the lateral and medial eustachian openings (Figure 6). Basisphenoid: The anterior portion of the basisphenoid is not preserved on any specimen. The posterior margin is moderately preserved in the specimen AMNH FARB 5061. It is thinly exposed ventral to the basioccipital, forming the posterior wall of the lateral and medial eustachian openings. Laterosphenoids: Only the dorsal laterosphenoid process is preserved on a single specimen (Figure 7). It connects to the ventral surface of the postorbital inset from the lateral margin, and reaches up into the supratemporal fenestra. Ventrally it connects to the prootic to fully enclose the supratemporal fenestra in palatal view. It also forms the anterior margin of the trigeminal foramen. Prootics: Only a posterior portion of the prootic is preserved on a single specimen (Figure 7). It forms the posterior margin of the trigeminal foramen and terminates ventrally with a short process. It stretches anteriorly to the anterior margin of the supratemporal fenestra in palatal view, reaching dorsally to form a wedge of exposed bone inside the fenestra. Exoccipitals: The exoccipitals meet medially with a straight suture ventral to the ventralmost point of the supraoccipital. They form the dorsal margin of the foramen magnum, flaring out posteriorly in a small lip. The exoccipitals then drop ventrally lateral to either side of the basioccipital. Along this ventral process in descending order are the cranial 27

Figure 6: Occipital view of Crocodylus megarhinus. bo, basioccipital; co, occipital condyle; eo, exoccipital; pa, parietal; q, quadrate; qj, quadratojugal; so, supraoccipital; sq, squamosal. Dashed lines indicate uncertainty is suture placement. Areas filled in with lines indicate plaster or epoxy repair. YPM VP-058532, Scale = 1 cm 28

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nerve XII, the vagus, and the lateral carotid foramen. Moving laterally the exoccipitals form a suture with the quadrates. Approximately half way to the lateral-most extent of the exoccipital, the exoccipital returns medially briefly to form the cranio-quadrate opening before moving laterally ultimately forming the end of the paraoccipital process (Figure 6). Supraoccipital: The supraoccipital is exposed on the dorsal surface of the skull table as a triangular wedge separating the posterior margin of the parietal. It forms an acute anterior point (Figures 3, 4). In occipital view the supraoccipital angles inward from the edge of the skull table and forms the medial margins of the posttemporal fenestrae. The ventral margins come together in a V to meet the exoccipitals (Figure 6). Palatines: The palatines terminate anteriorly at the posterior edge of the eighth maxillary alveoli, approximately level with the anterior-most tip of the suborbital fenestrae. The palatine-maxilla suture forms a rounded point, concave posteriorly. Laterally the sutures are more irregular. The palatine-maxilla suture intersects with the suborbital fenestrae at the level of the ninth maxillary alveoli. Beyond this the palatines narrow gradually forming a curved medial margin for the fenestrae. Posteriorly they begin to flare laterally. The sutures with the pterygoids are very irregular (Figure 8). Pterygoids: The pterygoids are oriented posteroventrally. Anteromedially they form a suture with the palatines. In connection with the palatines a narrow wedge of pterygoid creates a flared out structure intersecting the suborbital fenestrae medially. Directly posterior to the intersection of the four bones there are two shallow recesses separated by a narrow ridge through which the pterygoid-pterygoid suture runs. Two much larger, deeper recesses are located posterior to these also separated by a ridge straddling the 30

suture. The pterygoids completely surround the choana, and are pushed up around the anterior margin of the opening forming a ridge. They continue posterior to the choana to form small posterior processes oriented posteriorly. Lateroventrally the pterygoids form sutures with the ectopterygoids (Figure 8). Ectopterygoids: The ectopterygoids form the posterolateral margins of the suborbital fenestrae. A short spur of maxilla separates the anterior-most point of the ectopterygoid from the margin of the suborbital fenestrae. Posterior to the suborbital fenestrae they are oriented posteroventrally. The posterior-most tip does not reach the posterior margin of the ectopterygoid (Figure 8). Bones of the Lower Jaw Dentaries: The dentaries are gently curved and bow outwards briefly after the eighth alveolus, ending after the twelfth or thirteenth alveoli. Each dentary contains fifteen alveoli. The alveoli are circular to subcircular. The fourth alveolus is larger than the third and the two are separate. The largest alveolus posterior to the fourth is the tenth, and they decrease in size through the end of the row. The alveoli are spaced approximately evenly, though there are wider gaps between 1-2, 2-3, 7-8, and 8-9. Anteriorly the dentary teeth project anterodorsally. Small foramen are present sporadically along the medial edge of the alveoli. The dentaries form a long mandibular symphysis, reaching posteriorly to between the sixth and seventh alveoli. The bone to either side of the symphysis is pinched to form a small mound with the symphysis at its apex. The dentaries narrow posterolaterally and form the anterior margins of the external mandibular fenestrae (Figure 11). 31

Figure 7: Palatal view of Crocodylus megarhinus. j, jugal; ls, laterosphenoid; m, maxilla; pm, premaxilla; pro, prootic; q, quadrate; qj, quadratojugal. Areas filled in with lines indicate plaster or epoxy repair. YPM VP-058532, Scale = 10 cm 32

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Figure 8: Palatal view of Crocodylus megarhinus. ec, ectopterygoid; j, jugal; m, maxilla; pal, palatine; pm, premaxilla; pt, pterygoid; q, quadrate; qj, quadratojugal. Areas filled in with lines indicate plaster or epoxy repair. FARB AMNH 5061, Scale = 10 cm 34

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Figure 9: Palatal view of Crocodylus megarhinus. m, maxilla; pm, premaxilla. Dashed lines indicate uncertainty is suture placement. Areas filled in with lines indicate plaster or epoxy repair. NHMUK R. 3327, Scale = 10 cm 36

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Splenials: The splenials are long and do not participate in the mandibular symphysis, the anterior edge of the splenial passes ventral to the Meckelian groove. The splenial lacks an anterior perforation for the mandibular ramus of cranial nerve V. In dorsal view the splenials become visible posterior to the seventh alveoli. It is unclear how far posteriorly they extend or what shape the posterior edge takes as available specimens are either incomplete or reconstructed with epoxy or plaster. They abut the tooth row beginning between the eleventh and twelfth alveoli (Figure 11). Coronoids: There are no preserved coronoids on any observed specimen. Surangulars: The anterior processes of the surangulars are unequal, but they do not form a branch bordering the toothrows. The surangular-dentary suture intersects the external mandibular fenestra anterior to the posterodorsal corner. The surangular-angular suture intersects the external mandibular fenestra at the posterior angle, and the surangular forms the posterodorsal margin of the fenestra (Figure 10). The surangular-angular suture lingually meets the articular at the ventral tip, and the surangular is flush against the surangular. The surangular-articular suture is bowed strongly laterally within the glenoid fossa, and the surangular continues to the dorsal tip of the lateral wall of the glenoid fossa. The posterior surangular process extends to the posterior ends of the retroarticular processes. Angulars: The angular-surangular suture contacts the external mandibular fenestra at the posterior angle, and the angular forms the posterventral margin of the fenestra (Figure 10). The angular-surangular suture lingually meets the articular at the ventral tip. 38

Articulars: Lingually the articular meets the surangular-angular suture at its ventral tip. The articular is flush against the surangular, and the surangular-articular suture is bowed strongly laterally within the glenoid fossa. The surangular extends to the posterior end of the retroarticular process, which projects posterodorsally. The foramen aerum is located at the extreme lingual margin of the retroarticular process (Figure 11). 39

Figure 10: Lateral view of Crocodylus megarhinus. an, angular; ar, articular; d, dentary; san, surangular. Areas filled in with lines indicate plaster or epoxy repair. FARB AMNH 5095, Scale = 10 cm 40

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Figure 11: Dorsal view of Crocodylus megarhinus. ar, articular; d, dentary; san, surangular; sp, splenial. Areas filled in with lines indicate plaster or epoxy repair. FARB AMNH 5095, Scale = 10 cm 42

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CROCODYLUS ARTICEPS The holotype of C. articeps (C. 10036) was previously housed at the Egyptian Geological Museum. It was discovered through personal communication with Mohamed Abdel Gawad that the type specimen cannot be located, suggesting that it was likely lost or destroyed during the transportation of the museum to its current locality. The holotype consisted of the anterior portion of the skull, terminating midway through the orbits. There is a cast of the holotype (R. 3322) in The Natural History Museum collections, though the cast is not detailed enough for extensive sutural identification (Figure 12). All description is therefore a summary of the cast and the original description by Andrews (1905, 1906). There was also a nearly complete mandible (C. 10065) described by Andrews (1906) that he attributed to C. articeps, though it is clearly from a larger individual than that of the skull. This specimen was also unable to be located, so the cast at the NHMUK (R. 3323) is all we can observe. Of the referred material observed, every specimen is partial and unable to be positively identified as C. articeps. The external surface of all specimens is covered in shallow, irregular pits. The snout shape of C. articeps most closely resembles that of a slender-snouted crocodylian. The snout tapers rapidly towards the anterior, with the rostrum being narrow and mostly straight laterally. Dentary teeth occlude in line with the maxillary toothrow, and dentary tooth four occludes in a notch between the premaxilla and maxilla. The teeth are circular in cross section. 44

Figure 12: Dorsal view of Crocodylus articeps. j, jugal; m, maxilla; n, nasal; pf, prefrontal; pm, premaxilla. Dashed lines indicate uncertainty is suture placement. NHMUK R. 3322, Scale = 10 cm 45

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CHAPTER IV RESULTS A matrix including 57 taxa and 189 morphological characters was analyzed through TNT. A total of 60 trees were retained after 9,038,978 rearrangements. Each had a length of 307, a CI of 0.47, and a RI of 0.72. In Winclada a strict consensus of the trees resulted in 38 nodes collapsing (Figure 13). Initially the analysis was run with Crocodylus articeps (skull), created with coding only the cranial characters, and Crocodylus articeps (full), created by coding both cranium and lower jaw. In a comparison to the other taxa included in the matrix C. articeps was not precisely replicated, however it could not be excluded from select taxa such as Maroccosuchus zennaroi Jonet and Wouters 1977, Paratomistoma courti Brochu and Gingerich 2000, Tomistoma petrolica Yeh 1958, and Trilophosuchus rackhami Willis 1993. C. articeps was ultimately left out of this analysis as the fragmentary nature of the fossil lowered resolution and collapsed nodes. The low Bremer support scores and bootstrapping percentages are expected as the number of characters diagnosing these nodes is low. 47

Figure 13: Strict consensus of 60 equally optimal trees. Tree Length = 413, consistency index = 0.35, and retention index = 0.54. Numbers at nodes are bootstrap replicate percentages on the left side of the slash and Bremer supports on the right. 48

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CHAPTER V DISCUSSION The original coding for C. megarhinus drew information from C. articeps in addition to specimens identified as C. megarhinus because at the time they were considered synonymous. With information gathered from the undescribed YPM specimen the coding for C. megarhinus has been slightly altered from that of the eusuchian matrix obtained from Dr. Brochu. A full comparison between the original coding and the coding created for this work is found in Appendix D. Characters 89, 103, 146, 151, and 160 were previously uncoded. Characters 115, 123, 125, 128, and 137 changed character state in the new matrix. A comparison of C. megarhinus and C. articeps finds several differences. The overall shape of C. megarhinus is that of a generalized crocodilian while C. articeps is a slender-snouted crocodilian. The premaxillary region of C. megarhinus is completely rounded followed by an abrupt expansion of the maxillary region whereas the premaxillary region of C. articeps more closely resembles an elongated oval compressed laterally. The maxillary region of C. articeps starts off narrower than the premaxillae, also in contrast to C. megarhinus, and expands posteriorly very gradually. Of the preserved cranial openings the incisive foramen differs in that C. megarhinus has three posterior lobes while C. articeps only has two. The external naris is bisected posteriorly by anterior projections of the nasals in C. megarhinus, compared to C. articeps where the nasals terminate posterior to the external naris. Both species have five premaxillary alveoli but in the maxilla C. megarhinus has thirteen alveoli while C. articeps has fourteen. Having observed specimens attributed to C. megarhinus both larger and smaller 50

Figure 14: A, Dorsal view of Crocodylus articeps skull (1; Andrews, 1906). B, Lateral view (1A). C, Palatal view (1B). D, Dorsal view of Crocodylus articeps lower jaw (2). E, Lateral view (2A). an, angular; ar, articular; d, dentary; m, maxilla; n, nasal; orb, orbit; pal, palatine; pf, prefrontal; pm, premaxilla; san, surangular; sp, splenial. Modified from Andrews (1906) Plate XXII. A-C; GMCE C. 10036 D-E; GMCE C. 10065 51

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