The first true Adocus (Testudines, Adocidae) from the Paleogene of Asia

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1 This article was downloaded by: [Научная библиотека СПбГУ], [Pavel Skutschas] On: 04 September 2013, At: 05:07 Publisher: Taylor & Francis Informa Ltd Registered in England and Wales Registered Number: Registered office: Mortimer House, Mortimer Street, London W1T 3JH, UK Journal of Vertebrate Paleontology Publication details, including instructions for authors and subscription information: The first true Adocus (Testudines, Adocidae) from the Paleogene of Asia Igor G. Danilov a, Elena V. Syromyatnikova a, Pavel P. Skutschas b, Tatyana M. Kodrul c & Jianhua Jin d a Zoological Institute of the Russian Academy of Sciences, Universitetskaya Emb 1, St. Petersburg, , Russia b Saint Petersburg State University, Universitetskaya Emb. 7/9, St. Petersburg, , Russia c Geological Institute of the Russian Academy of Sciences, Pyzhevsky Lane 7, Moscow, , Russia d School of Life Sciences, Sun Yat-sen University, Guangzhou, , China To cite this article: Igor G. Danilov, Elena V. Syromyatnikova, Pavel P. Skutschas, Tatyana M. Kodrul & Jianhua Jin (2013) The first true Adocus (Testudines, Adocidae) from the Paleogene of Asia, Journal of Vertebrate Paleontology, 33:5, To link to this article: PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the Content ) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at

2 Journal of Vertebrate Paleontology 33(5): , September by the Society of Vertebrate Paleontology ARTICLE THE FIRST TRUE ADOCUS (TESTUDINES, ADOCIDAE) FROM THE PALEOGENE OF ASIA IGOR G. DANILOV, 1 ELENA V. SYROMYATNIKOVA, 1 PAVEL P. SKUTSCHAS, 2 TATYANA M. KODRUL, 3 and JIANHUA JIN *,4 1 Zoological Institute of the Russian Academy of Sciences, Universitetskaya Emb 1, St. Petersburg, , Russia, igordanilov72@gmail.com; esyromyatnikova@gmail.com; 2 Saint Petersburg State University, Universitetskaya Emb. 7/9, St. Petersburg, , Russia, skutchas@mail.ru; 3 Geological Institute of the Russian Academy of Sciences, Pyzhevsky Lane 7, Moscow, , Russia; 4 School of Life Sciences, Sun Yat-sen University, Guangzhou, , China, lssjjh@mail.sysu.edu.cn ABSTRACT This paper describes a new species of the genus Adocus (A. inexpectatus, sp. nov.), based on an almost complete shell from the upper Eocene Youganwo (= Youkanwo) Formation of the Maoming Basin, China. The inclusion of A. inexpectatus in a phylogenetic analysis of Adocusia resulted in a polytomy with Adocus aksary and A. amtgai (both from the Upper Cretaceous of Asia). This clade formed a polytomy with the North American species of Adocus. Like other true Adocus, A. inexpectatus has overlapping of the marginals onto the costals in the middle and posterior parts of the carapace and sculpturing of the shell surface with small grooves and pits. Thus, A. inexpectatus represents the first true Adocus from the Paleogene of Asia. Other specimens from the Paleogene of Asia that have been referred to Adocus, characterized by shell sculpturing with small dots and unknown condition of the marginal/costal overlapping, are distinct from true Adocus and herein referred to as Adocus spp. Here we also report the presence of Adocus from the Paleocene of North America. Our study indicates that the evolutionary and biogeographic history of the Adocidae was more complicated than considered previously, including previously unrecognized dispersal events between Asia and North America. SUPPLEMENTAL DATA Supplemental materials are available for this article for free at INTRODUCTION Adocidae Cope, 1870, is a group of freshwater cryptodiran turtles, known mainly from the Cretaceous and Paleogene of Asia and North America (Hutchison, 2000; Sukhanov, 2000; Danilov et al., 2011). According to modern phylogenetic studies (Danilov and Syromyatnikova, 2009a, 2009b; Syromyatnikova, 2011; Syromyatnikova et al., 2012), Adocidae includes Yehguia tatsuensis (Ye, 1963) from the Upper Jurassic of China, which is the sister taxon to a clade uniting all other adocids, consisting of Adocus Cope, 1868a (Adocinae Cope, 1870; Cretaceous early Oligocene of Asia; Late Cretaceous Paleocene of North America), and a clade uniting the genera Ferganemys Nessov and Khosatzky, 1977a, and Shachemys Kuznetsov, 1976 (Shachemydinae Khosatzky in Nessov and Khosatzky, 1977b; Cretaceous of Asia). The genus Adocus is diagnosed by overlapping of the marginals onto the costals in the middle and posterior parts of the carapace (synapomorphy of Adocus), whereas other adocids either have overlapping of the marginals onto the costals only in the middle part of the carapace (Yehguia tatsuensis) or have no such overlapping, i.e., the marginals are restricted to the peripherals (Ferganemys spp., Shachemys spp.). Traditionally, Adocus unites, in addition to relatively well-known species from the Cretaceous of Asia and North America and from the Paleocene of North America (hereinafter true Adocus), a number of problematic forms from the Paleogene of Asia (Gilmore, 1931; Chkhikvadze, 1973; Danilov et al., 2011). These problematic forms are represented by very incomplete material, and referred to as Adocus spp. (see Danilov et al., 2011). Among these forms * Corresponding author. are Adocus kazachstanica Chkhikvadze, 1973 (Zaisan Basin, Kazakhstan; middle Eocene), A. orientalis Gilmore, 1931 (Telegraph Line Camp, China; Ergil Obo, Mongolia; upper Eocene), cf. A. orientalis (North Mesa, China; upper Eocene), Adocus sp. indet. 1 (Aktau, Kazakhstan;?Oligocene), Adocus sp. indet. 2 (Urtyn Obo, China; lower Oligocene), and Adocus sp. indet. (Dzhylga, Kazakhstan; upper Paleocene) (see Fig. 1). The synapomorphic character of the genus Adocus, i.e., overlapping of the marginals onto the costals in the middle and posterior parts of the carapace, is not known in Adocus spp. In addition, Adocus spp. have shell sculpturing with small dots, whereas true Adocus has sculpturing with small grooves and pits (Fig. 2; Danilov et al., 2011). This paper describes a new species of the genus Adocus (A. inexpectatus, sp. nov.), based on an almost complete shell from the upper Eocene Youganwo (= Youkanwo) Formation of the Maoming Basin of China (Fig. 1). This specimen was purchased by the School of Life Sciences of Sun Yat-sen University (Guangzhou, China) from a local amateur fossil collector in Our phylogenetic analysis places this new species in a clade with two species of Adocus from the Upper Cretaceous of Asia. Because A. inexpectatus, sp. nov., has the synapomorphic character (overlapping of the marginals onto the costals in the middle and posterior parts of the carapace) and the sculpturing of true Adocus, it represents the first true Adocus from the Paleogene of Asia. This fact sheds new light on the evolutionary and biogeographic history of the genus Adocus and the family Adocidae in general. Finally, the new species of Adocus adds to the list of vertebrates from the Youganwo Formation. Institutional Abbreviations AMNH, American Museum of Natural History, New York, New York, U.S.A.; MMT, turtle collection from the Maoming Basin in the School of Life Sciences, Sun Yat-sen University, Guangzhou, China; PIN, 1071

3 1072 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 33, NO. 5, 2013 FIGURE 1. Map (above) showing the geographic distribution of Paleogene Adocus in Asia and chart (below) showing the temporal and geographic distribution of the Paleogene Adocus from Asia and North America. Key: A, Adocus sp. indet., Dzhylga, Kazakhstan; late Paleocene; B, Adocus sp. indet. 1, Aktau, Kazakhstan;?Aktau Formation,?Oligocene; C, Adocus kazachstanica, Zaisan Basin, Kazakhstan; Obayla Formation, middle Eocene; D, Adocus orientalis, Ergil Obo, Mongolia; Ergiliin Dzo Formation, late Eocene; E, Adocus orientalis, Telegraph Line Camp, China; Irdin Manha Formation, late Eocene; cf. Adocus orientalis, North Mesa, China; Ulan Shireh Formation, late Eocene; Adocus sp. indet. 2, Urtyn Obo, China; Ulan Gochu Formation, early Oligocene; F, Adocus inexpectatus, Maoming City, China; Youganwo Formation, late Eocene. See Danilov et al. (2011) for details about localities other than Maoming City. Borissyak Paleontological Institute of the Russian Academy of Sciences, Moscow, Russia; UCMP, University of California Museum of Paleontology, Berkeley, California, U.S.A.; YPM, Yale Peabody Museum, New Haven, Connecticut, U.S.A.; ZIN PH, Paleoherpetological collection, Zoological Institute of the Russian Academy of Sciences, St. Petersburg, Russia. GEOLOGIC SETTING AND ASSOCIATED VERTEBRATE ASSEMBLAGE The Maoming Basin is an asymmetric northwestly southeastly elongated upper Mesozoic Cenozoic sedimentary basin nearly 40 km long and 16 km wide, located in southwest Guangdong Province, South China. The Upper Cretaceous Neogene

4 DANILOV ET AL. PALEOGENE ADOCUS FROM ASIA 1073 FIGURE 2. Shell sculpturing in Adocus. A, Adocus kizylkumensis (ZIN PH S78-1); Sultanuvais Range, Uzbekistan; upper part of the Khodzhakul Formation, early Cenomanian; B, Adocus inexpectatus (MMT 001), Maoming City, Maoming Basin, Guangdong Province, China; Youganwo Formation, late Eocene; C, cf. Adocus orientalis (AMNH 6712), North Mesa, Chimney Butte Quarry, Shara Murun region, Inner Mongolia, China; Ulan Shireh Formation, late Eocene; D, Adocus sp. (UCMP V76168), Turtle Tease locality, Montana, U.S.A.; middle Paleocene. Scale bar equals 10 mm. sedimentary sequence of the Maoming Basin is subdivided into eight formations (Fm.), which are in ascending stratigraphic order: Sanyajiang Fm., Tongguling Fm., Shangdong Fm., Youganwo Fm., Huangniuling Fm., Shangcun Fm., Laohuling Fm., and Gaopengling Fm. (Nan and Zhou, 1996). All known vertebrate remains from the Maoming Basin were found in dark brown oil shales in the upper part of the Youganwo Formation, which were deposited in lacustrine conditions. The Youganwo Formation has been dated as late Eocene based on fossil reptiles, fishes, mammals, and palynomorph assemblages (Jin, 2008). The vertebrate assemblage of the Youganwo Formation is diverse and includes the cyprinid fish Cyprinus maomingensis Liu, 1957, the carettochelyid turtleanosteira maomingensis Chow and Liu, 1955, the geoemydid turtle Isometremys lacuna Chow and Ye, 1962, a new geoemydid turtle Guandongemys pingi Claude et al., 2012, and the trionychid turtle Trionyx impressus Ye, 1963, the tomistomine crocodile Tomistoma petrolica Ye, 1958, the alligatorid crocodile Alligatoridae, gen et sp. indet., and the chalicotherioid mammal Lunania cf. youngi Chow, 1957 (Chow and Liu, 1955; Liu, 1957; Ye, 1958, 1963, 1994; Chow and Ye, 1962; Wang et al., 2007; Tong et al., 2010; Claude et al., 2012; Skutschas et al., in press). MATERIALS AND METHODS In addition to the new species described below, our study relies on published data and personal observations on the following adocid taxa: Adocus agilis Cope, 1868a, from the Upper Cretaceous of the U.S.A. (AMNH 1466; Hay, 1908); Adocus aksary Nessov in Nessov and Krasovskaya, 1984, from the Upper Cretaceous of Uzbekistan (see Syromyatnikova and Danilov, 2009); Adocus amtgai Narmandakh, 1985, from the Upper Cretaceous of Mongolia (PIN , ; Syromyatnikova et al., 2011; unpubl. data); Adocus annexus Hay, 1910, from the Paleocene of the U.S.A. (Hay, 1910; Gilmore, 1919); Adocus beatus (Leidy, 1865) from the Upper Cretaceous of the U.S.A. (AMNH 1138, 1350; YPM 782; Hay, 1908; White, 1972; I.G.D., pers. observ. of YPM 782, holotype of Adocus punctatus Marsh, 1890); Adocus bossi Gilmore, 1919, from the Upper Cretaceous of the U.S.A.; A. foveatus Nessov and Khosatzky in Khosatzky and Nessov, 1977, from the Upper Cretaceous of Tajikistan (see Syromyatnikova and Danilov, 2009); Adocus kirtlandius Gilmore, 1919; Adocus kizylkumensis Nessov, 1981, from the Upper Cretaceous of Uzbekistan (see Syromyatnikova and Danilov, 2009); Adocus orientalis from the upper Eocene of China and Mongolia (AMNH 6356; Gilmore, 1931; Danilov et al., 2011); Adocus sp. from the Upper Cretaceous of the U.S.A. (Meylan and Gaffney, 1989); Adocus substrictus Hay, 1908, from the Paleocene of the U.S.A. (AMNH 1204); Adocus syntheticus Cope, 1870, from the Upper Cretaceous of the U.S.A. (Hay, 1908). In order to determine the phylogenetic position of Adocus inexpectatus, we performed a phylogenetic analysis of Adocusia Danilov and Parham, 2006, using the modified character-taxon matrix of Danilov and Syromyatnikova (2009a, 2009b) with additions from Syromyatnikova (2011). The following modifications to this character-taxon matrix were made: we added A. amtgai, A. bossi, anda. kirtlandius in our analysis. These three species are among the best-known members of the genus and with most portions of the shell preserved. We added to the analysis three additional characters: character 76, width of vertebral 5: (0) as wide as more anterior vertebrals or wider, (1) narrower than more anterior vertebrals; character 77, marginals overlapping onto the costals: (0) beginning with marginal 5, (1) beginning with marginal 3 or 4; and character 78, shape of anterior lobe of the plastron: (0) rounded, (1) truncated (see Appendix 1 for scorings of these new characters and Appendix 2 for characters coded for A. amtgai, A. bossi, A. inexpectatus,anda. kirtlandius). The final data matrix includes 78 osteological characters for 27 taxa (see Supplemental Data). Our updated matrix was assembled using NDE (Page, 2001) and analyzed with NONA version 2 and Winclada version by Ratchet algorithm with 1000 iterations. Characters were left unordered and considered reversible and of equal weight. Support for each node was measured by calculating bootstrap frequencies (Felsenstein, 1985) and Bremer supports (Eriksson, 1998). Anatomical terms for the shell follow Zangerl (1969) and Hutchison and Bramble (1981). SYSTEMATIC PALEONTOLOGY TESTUDINES Batsch, 1788 CRYPTODIRA Cope, 1868b ADOCUSIA Danilov and Parham, 2006 ADOCIDAE Cope, 1870 ADOCUS Cope, 1868a ADOCUS INEXPECTATUS, sp. nov. (Fig. 3) Etymology Inexpectatus, Latin for unexpected, in reference to the fact that we did not expect to find new turtle taxa when we started our study of the vertebrate collections from the Maoming Basin. Holotype MMT 001, an incomplete shell. Locality and Horizon The oil shale quarry (21 42 N, E) located near Maoming City, Maoming Basin, Guangdong Province, China; Youganwo Formation, upper Eocene. Diagnosis A species of Adocus, which can be differentiated from all other species of the genus by shorter vertebral 1, vertebral 4 overlapping onto suprapygal 1, and long medial borders of the extragulars. In addition, it can be differentiated from other species of the genus by elongated neural 6 (except A. amtgai and A. beatus), vertebral 5 narrower than more anterior vertebrals

5 1074 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 33, NO. 5, 2013 (except A. aksary, A. amtgai, and A. bossi), and overlapping of marginals onto costals beginning with marginal 4 (except A. aksary and A. amtgai). In addition, it can be differentiated from A. beatus by the rounded anterior lobe of the plastron; from A. orientalis by the rounded anterior lobe of the plastron, larger extragulars, and shell sculpturing with small grooves and pits. See Table 1 for a more detailed comparison. DESCRIPTION Shell The holotype shell (Fig. 3) consists of an incomplete carapace (devoid of the right portion of the nuchal, suprapygal 2, the pygal, lateral portions of costals 5 8, and most peripherals) and the complete plastron. In some areas, the periphery of the shell is represented by mess of disarticulated plate fragments and was restored by the fossil collector. The length of the shell is estimated at about 350 mm. Its shape is reconstructed as an elongate oval, probably wider posteriorly than anteriorly. Some plates of the shell are slightly disarticulated along the sutures. The plastron is estimated to be approximately 80% of the carapace length and does not reach the carapace rim anteriorly. The surface of the shell is covered with the typical sculpturing of Adocus, consisting of small grooves and pits. Scale sulci are narrow and shallow. Measurements of the shell are given in Table 2. Carapace The anterior edge of the carapace is truncated, with a very small nuchal emargination. The nuchal was hexagonal, wider than long, and with a relatively wide anterior border (ratio of the nuchal anterior width to its maximum width is estimated to be 0.6). The anterolateral border of the nuchal is almost equal to its posterolateral border. The posterior border of the nuchal is concave and contacts neural 1. There are six neurals, all of which are longer than wide. Neural 1 is the largest, hexagonal and short-sided posteriorly, and has a slight waist in the middle part. Neural 2 is relatively small and tetragonal. Neurals 3 5 are hexagonal and short-sided anteriorly. Neural 6 is heptagonal, and slightly wedge-shaped between the seventh costals. Among Adocus spp., a similarly shaped neural 6 is present in A. amtgai and A. beatus, whereas in other species, neural 6 is relatively shorter and is hexagonal or pentagonal. The suprapygals are represented by a complete suprapygal 1, whereas suprapygal 2 is not preserved. Suprapygal 1 is relatively small and oval, slightly longer than wide. The shape of suprapygal 1 is similar to that in A. aksary, A. amtgai, A. beatus, anda. kirtlandius.inotheradocus, this element is absent or unknown. The costals are almost fully preserved, except for the lateral parts of the right costals 1 and 5 8. Costals 2 and 4 are longer medially than laterally, whereas costals 3 and 5 8 are longer laterally than medially. Costals 7 and 8 contact each other at the midline. The peripherals are represented only by complete left peripherals 1 and 2, and by fragments of left peripherals 3 and 4. These elements have no specific peculiarities; their free borders are slightly upturned as in most other Adocus spp. The scales of the carapace are well preserved, except the cervical, lateral parts of most of the marginals, and the posterior part of vertebral 5. Vertebral 1 is widened anteriorly, contacts marginal 2 and has rounded (convex) lateral borders. The length of vertebral 1 is about 50% of its width, which is shorter than in other Adocus spp., in which the length of vertebral 1 is about 65% or more of its width. Vertebrals 2 4 are longer than wide, much narrower than vertebral 1, and almost rectangular (vertebrals 2 and 3) or heptagonal (vertebral 4). Vertebral 4 is divided into two parts by an oblique sulcus, which extends from the left part of the anterior border of vertebral 4 to the middle of its right posterolateral border. The posterior border of vertebral 4 forms a small projection overlapping suprapygal 1. Vertebral 5 is represented only by its anterior part, but was clearly narrower than vertebrals 2 4. A similarly narrow vertebral 5 is known in Adocus aksary and A. bossi, whereas in other Adocus spp. it is wider than the more anterior scales. The pleurals are relatively narrow and become narrower anteroposteriorly, as in other species of Adocus. The ratio of pleural 2 width to its length is about 0.6. The pleurals are asymmetrical: right pleural 1 extends more laterally than the left one, and overlaps costal 3 by a narrow lappet; left pleural 4 is divided into two equal parts by the transverse sulcus passing across the middle of costal 7. The marginals are represented only by complete left marginals 1 3 and by medial parts of other marginals, except marginal 12, which are not preserved. Marginals 1 3 are restricted to the peripherals and cover about two-thirds of their external surface. Marginals 4 11 overlap onto costals 1 8, respectively, and cover about one-third of their width. In most other species of Adocus, the overlapping of the marginals onto the costals begins with marginal 5, whereas in A. aksary and A. amtgai it begins with marginal 3 or 4. Plastron The anterior lobe of the plastron is wider than long (the ratio of its midline length to the width at the base is about 0.5), and is rounded anteriorly. In other species of Adocus, the anterior lobe is rounded (A. annexus, A. bossi, A. kirtlandius, A. substrictus) or truncated (A. amtgai, A. beatus, A. syntheticus, A. orientalis). The length of the anterior lobe makes up about 30% of the plastron length. A similar contribution of the anterior lobe to the plastron length is present in A. amtgai and A. annexus, whereas in other species of Adocus the anterior lobe is relatively short. The posterior lobe is relatively longer and narrower at the base (ratio of its midline length to the width at the base is estimated as 0.7) than the anterior one, and rounded posteriorly. The length of the bridge of the plastron is about 43% of the plastron length. Gular and anal notches are absent as in other species of Adocus. The epiplastron has a rounded anterior border, which is less than the length of the, as is also the case in A. aksary and A. bossi. The entoplastron is hexagonal, with poorly developed lateral borders, and is wider than long. The hyoplastra and hypoplastra make almost equal contributions to the bridge length. The left hyoplastron and the right hypoplastron have a long contact that separates the right hyoplastron from the left hypoplastron. The xiphiplastron is almost as wide as long, and is rounded at its posterior border. The length of the xiphiplastron is about 62% of the posterior lobe length at the midline. The plastral scales are represented by the gulars, extragulars, humerals, pectorals, abdominals, femorals, anals, and four pairs of inframarginals. The gulars are asymmetrical: the left gular is long and overlaps the entoplastron as well as the posterior part of the right epiplastron, whereas the right gular is short and does not reach the entoplastron. The gulars are relatively narrow; their anterior width is less than the length of the, as in A. aksary and A. orientalis, whereas in other species of Adocus the gulars are relatively wider. The extragulars are relatively large, covering about one-third of the external surface of the epiplastra, with long medial borders that exceed the length of the. In all other species of Adocus, the extragulars have short medial borders, which are less than the length of the. The pectorals are relatively narrow (their medial length is about one-third of the length of the abdominals), slightly overlapping the entoplastron. The pectorals of other species of

6 TABLE 1. Comparison of shell characters among some Late Cretaceous and Paleogene species of Adocus. Characters A. aksary A. amtgai A. beatus A. bossi A. inexpectatus A. kirtlandius A. orientalis Length of the shell 400 mm 400 mm 500 mm 700 mm 350 mm 500 mm 550 mm Nuchal emargination Weak Weak Weak or absent Absent Weak or absent?? Number of neurals Six Six Six or seven Six Six Six? Neural 6 Shortened Elongated Elongated Shortened Elongated Shortened? Number of suprapygals Two Two Two One Two Two? Width of anterior border of epiplastron Less than length of Cervical Lens or trapezoid, expanded anteriorly or posteriorly Ratio of width of vertebral 1 to its length Vertebral 5 Narrower than anterior vertebrals More than length of Trapezoid, expanded anteriorly More than length of Trapezoid, expanded anteriorly More than length of Trapezoid, expanded posteriorly Less than length of? More than length of??? ?? Narrower than anterior vertebrals Pleurals 2 4? Narrow (width makes up 30% of length) Marginals overlapping costals Anterior edge of anterior lobe of plastron Ratio of length of anterior lobe to length of plastron Width of anterior edge of gulars Extension of gulars onto entoplastron Ratio of length of extragular medial border to length of Pectorals extension onto the entoplastron Beginning with marginal 3 or 4 Beginning with marginal 4 Equal or wider than anterior vertebrals Wide (width makes up 60% of length) Beginning with marginal 5 Narrower than anterior vertebrals Wide (width makes up 60% of length) Beginning with marginal 5 Narrower than anterior vertebrals Wide (width makes up 60% of length) Beginning with marginal 4 Equal or wider than anterior vertebrals Wide (width makes up 60% of length) Beginning with marginal 5 Truncated Truncated Truncated Rounded Rounded Rounded Rounded Less than length of ? More than length of More than length of Variable Less than length of epiplastal? Equal to length of Present or absent Present Present or absent Present Present? Present >1? 1 Present or absent Present Present Absent Present Absent Present Number of inframarginals? Three or four pairs Four pairs Three pairs Four pairs Four pairs Four pairs Inframarginals? Relatively wide Relatively narrow Relatively narrow Relatively Relatively wide Relatively narrow narrow Shell sculpturing With small grooves and pits With small grooves and pits With small grooves and pits With small grooves and pits With small grooves and pits With small grooves and pits??? With small dots estimated. 1075

7 1076 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 33, NO. 5, 2013 FIGURE 3. Adocus inexpectatus (MMT 001), an incomplete shell; Maoming City, Maoming Basin, Guangdong Province, China; Youganwo Formation, upper Eocene. Specimen in A, dorsal, and B, ventral views. Explanation drawing in C, dorsal, and D, ventral views. Dark gray indicates matrix; light gray indicates the part of the shell restored by the local collector; hatching indicates broken surfaces; dashed line indicates shell outline. Abbreviations: abd, abdominal; an, anal; c, costal; ce, central; egu, extragular; ent, entoplastron; epi, epiplastron; fe, femoral; gu, gular; hu, humeral; hyo, hyoplastron; hypo, hypoplastron; im, inframarginal; m, marginal; n, neural;nu, nuchal; p, peripheral; pe, pectoral;ple, pleural;sp, suprapygal; xi, xiphiplastron. Arabic numerals designate element numbers.

8 DANILOV ET AL. PALEOGENE ADOCUS FROM ASIA 1077 TABLE 2. Measurements (in mm) of the shell of Adocus inexpectatus (MMT 001). Characters Measurements Nuchal (length/width) 44.0/ 62 Neurals (length/width) Neural /26.8 Neural /15.8 Neural /20.5 Neural /21.1 Neural / 21.0 Neural /20.4 Suprapygal 1 (length/width) 20.8/16.2 Costal 1 (medial length/lateral 34.0/ 65.1/49.5/ 71.7 (l) length/maximal length/posterior width) Costals 2 8 (medial length/lateral length/posterior width) Costals /23.8/78.4 (l) Costal / 43.8/84.7 (l) Costal /23.3/82.4 (l) Costal / 43.6/ 78.1 (l) Costal /30.2/ 68.3 (l) Costal / 30.3/59.4 (l) Costal / 20.1/45.6 (l) Vertebrals (length/width) Vertebral / 90 Vertebral /52.2 Vertebral /56.2 Vertebral /46.9 Vertebral 5?/ 44 Pleurals (medial length/lateral length/posterior width) Pleural /?/38.9l Pleural /72.2/38.1 (l) Pleural /54.3/32.5 (l) Pleural /58.0/21.9 (l) Plastron (length along the midline/width 290/ 190 at the hyo-hypoplastral suture) Epiplastron (length medial) 23.7s, 23.1 (r) Entoplastron (length/width) 40.7/51.5 Hyoplastron (length medial) 45.1 (r) Hypoplastron (length medial) 80.5 (r) Xiphiplastron (length medial) 51.8 (r) Gulars (length medial) 33 (l) Extragulars (length medial) 22 (l) Humerals (length medial) 36 (l) Pectorals (length medial) 30 (l) Abdominals (length medial) 88 (l) Femorals (length medial) 60 (l) Anals (length medial) 37 (l) Inframarginals (length at contact with plastral scales/width at contact with anterior scales) Inframarginal 1 10 (l), 10 (r)/ Inframarginal 2 72 (l), 41 (r)/ 8 (l), 8 (r) Inframarginal 3 23 (l), 63 (r)/ 12 (l), 10 (r) Inframarginal 4 19 (l), (r)/ 10 (l), 13 (r)?, element unmeasurable;, element not preserved; (r) and (l) designate right and left measurements, respectively. Adocus are variable: overlapping (A. annexus and A. beatus) or not overlapping the entoplastron (Adocus agilis, A. bossi, A. kirtlandius, A. orientalis,anda. substrictus). The abdominals are long. They contribute to the rim of the inguinal notch on the right side, but not on the left side. The inframarginals are represented by four pairs of narrow scales that barely extend onto the peripherals (except inframarginals 1 and 4). On the right side, the plastral part of inframarginal 1 is small. The right inframarginal 2 is relatively small, and restricted to the hyoplastron, whereas the left inframarginal 2 is larger and overlaps the hypoplastron. Both inframarginal 2 s have narrow contacts with the first inframarginals and wider contacts with the third inframarginals. Inframarginal 3 is large and overlaps the hyoplastron on the right-hand side, but is small and restricted to the hypoplastron on the left side. Both of the third inframaginals are about equally wide anteriorly and posteriorly. The fourth inframarginals are narrower anteriorly than posteriorly. In other Adocus, the inframarginals are usually represented by four pairs (except A. bossi, which has three pairs), and are relatively narrow (A. agilis, A. bossi, A. beatus, A. syntheticus, and A. orientalis)orwide(a. amtgai, A. annexus, A. kirtlandius,and A. substrictus). The midline sulcus of the plastron is strongly sinuous between the pectorals, abdominals, femorals, and anals, as in most other species of Adocus. DISCUSSION We assign Adocus inexpectatus to the Adocidae based on two synapomorphies: the typical adocid shell sculpturing with relatively small and regular grooves and pits, and shallow and narrow scale sulci (see Danilov and Syromyatnikova, 2009a, 2009b; Danilov et al., 2011). The new species is assigned to the genus Adocus based on a single observable synapomorphy the marginals overlap onto the costals in the middle and posterior parts of the carapace (Danilov and Syromyatnikova, 2009a, 2009b; Syromyatnikova and Danilov, 2009). The shell sculpturing of Adocus inexpectatus is similar to the Cretaceous members of Adocus ( true Adocus) and different from the Paleogene Asiatic forms sometimes referred to this genus, but now considered as Adocus spp. (see Danilov et al., 2011). Among true Adocus, A. inexpectatus is most similar to A. aksary and A. amtgai (both from the Upper Cretaceous of Asia) in that it has a narrow vertebral 5 (narrower than the anterior vertebrals) and the overlapping of the marginals onto the costals begins with marginal 4. For differences between A. inexpectatus and the other species of Adocus see Diagnosis and Table 1. The result of our phylogenetic analysis consists of 69 most parsimonious trees with lengths of 149 steps, a consistency index of 0.57, and a retention index of A strict consensus of these trees is shown in Figure 4. According to our phylogenetic analysis, Adocus inexpectatus belongs to an Asiatic clade that includes A. aksary and A. amtgai. This clade is supported by two synapomorphies, a narrow vertebral 5, and the overlapping of the marginals onto the costals beginning at the level of marginal 3 or 4. Within this clade, all three species form a polytomy. Other species of Adocus included in the analysis (all from North America) form a polytomy at the base of the Adocus clade. The topology of the rest of the tree agrees with our previous analysis (Danilov and Syromyatnikova, 2009a, 2009b). An important result of our analysis is the recognition of the distinct clade of Asiatic Adocus, consisting of A. aksary, A. amtgai, anda. inexpectatus. In addition to the members of this clade, there are other species of Adocus in Asia, characterized by the overlapping of the marginals onto the costals beginning at the level of marginal 5 (A. foveatus, A. kizylkumensis) or unknown for this and other important characters (see Syromyatnikova and Danilov, 2009). In all North American Adocus, inwhichthis character is observable, the marginals overlap onto the costals beginning with marginal 5. The character of costal overlap beginning at the level of marginal 5 is considered to be primitive in our analysis. According to the latest review of Asian adocids (Danilov et al., 2011), the group is known in Asia from the Late Jurassic Campanian, and then disappeared until the late Paleocene late Oligocene. In North America, adocids are known from the Coniacian Paleocene without a gap (Hutchison, 2000). The paraphyly of Asian adocids has been demonstrated by several phylogenetic analyses (Danilov and Syromyatnikova, 2009a, 2009b; Syromyatnikova, 2011; Syromyatnikova et al., 2012; this paper) and suggests that Adocus has an Asian origin and migrated into North America during the Cretaceous. The

9 1078 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 33, NO. 5, 2013 reappearance of adocids in Asia in the Paleogene as Adocus spp. was suggested to be a result of its immigration from North America (Danilov et al., 2011). The possible relationships of the Paleogene Adocus spp. of Asia with North American forms are supported by a recent observation by one of us (E.V.S.) of the Adocus -type sculpturing in some fragmentary specimens referred to as Adocus sp. from the middle Paleocene of the U.S.A. (Fig. 2; Turtle Tease, Montana; UCMP V76168). Unfortunately, the condition of the marginal-costal overlapping, which would help to resolve their relationships, is unknown for these specimens. The discovery of the true Adocus in the Paleogene of Asia (Adocus inexpectatus) suggests that the Late Cretaceous gap in the Asian record of the adocids is not real and that some true Asian adocids survived into the Paleogene. In this case, the origin of the Adocus -type forms in the Paleogene of Asia and North America may have three possible explanations: (1) their dispersal from North America to Asia; (2) their dispersal from Asia to North America; and (3) their independent origin in North America and Asia. The incompleteness of the material of the Adocus -type forms prevent us from accepting any of these hypotheses until new finds allow inclusion of the Adocus -type forms into phylogenetic analyses. In any case, our study shows that the evolutionary and biogeographic history of the Adocidae was more complicated than considered previously, including previously unrecognized dispersal events between Asia and North America. The discovery of Adocus in the upper Eocene of Maoming Basin of southern China expands the geographic distribution of this genus in Asia to southern China, and contradicts a previously suggested hypothesis about the latitudinal distribution of Adocus (see Danilov et al., 2011). At the same time, this result means that we should expect new finds of Adocus in southern regions of Asia within the Late Cretaceous Paleogene. Although the Maoming Basin has been known for its fossil vertebrates since the 1950s, discoveries of new material and taxa during the last decade (Wang et al., 2007; Tong et al., 2010; Claude et al., 2012; Skutschas et al., in press; this paper) show that the diversity of the Maoming vertebrate assemblage in general, and its turtle assemblage in particular, is underestimated. This must inspire future researchers on the Maoming Basin to continue to search for fossil vertebrates, which could lead to the discovery of new turtle taxa. FIGURE 4. Phylogeny of Adocidae showing the hypothesized position of Adocus inexpectatus. This is a strict consensus tree of 69 most parsimonious trees (see Discussion for description). Numbers above nodes are bootstrap support values obtained from 1000 replicates. Numbers below nodes are Bremer support indices. ACKNOWLEDGMENTS The authors thank D. Brinkman (Royal Tyrrell Museum of Paleontology, Drumheller, Canada) and T. Lyson (YPM) for reviewing the paper and useful comments. This study was supported by the National Natural Science Foundation of China (grants and ), the joint Project of National Natural Science Foundation of China and Russian Foundation for Basic Research (grants , , , GFEN a, and mol a), the Key Project of the Sun Yat-sen University for inviting foreign teachers, and the grant of the President of the Russian Federation to the Leading Scientific Schools (no. NSh ). LITERATURE CITED Batsch, A. J. G. C Versuch einer Anleitung, zur Kenntniß und Geschichte der Thiere und Mineralien. Akademische Buchhandlung, Jena, 528 pp. Chkhikvadze, V. M [Tertiary Turtles of the Zaissan Depression]. Metsniereba Publishers, Tbilisi, 100 pp. [Russian] Chow, M On some Eocene and Oligocene mammals from Kwangsi and Yunnan. Vertebrata PalAsiatica 1(3): Chow, N. N., and C. L. Liu A new anosterine turtle from Maoming, Kwangtung. Vertebrata PalAsiatica 6: [Chinese ; English ] Chow, M.-C., and X.-K. Ye A new emydid from Eocene of Maoming, Kwangtung. Vertebrata PalAsiatica 6: [Chinese ; English ] Claude, J., J.-Y. Zhang, J.-J. Li, J.-Y. Mo, X.-W. Kuang, and H. Tong Geoemydid turtles from the late Eocene Maoming Basin, Southern China. Bulletin de la Société géologique de France 183: Cope, E. D. 1868a. On some Cretaceous Reptilia. Proceedings of the Academy of Natural Sciences of Philadelphia 20: Cope, E. D. 1868b. On the origin of genera. Proceedings of the Academy of Natural Sciences of Philadelphia 20: Cope, E. D On the Adocidae. Proceedings of the American Philosophical Society 11: Danilov, I. G., and J. F. Parham A redescription of Plesiochelys tatsuensis from the Late Jurassic of China, with comments on the antiquity of the crown clade Cryptodira. Journal of Vertebrate Paleontology 26: Danilov, I. G., and E. V. Syromyatnikova. 2009a. [Phylogenetic analysis of turtles of the superfamily Adocoidea]; pp in A. Y.

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Notulae Naturae 447:1 10. Ye, H.-K A new crocodile from Maoming, Kwangtung. Vertebrata PalAsiatica 2: [Chinese ; English ] Ye, H.-K Fossil turtles of China. Paleontologica Sinica, New Series C 18: [Chinese 1 78; English ] Ye, H.-K Fossil and Recent Turtles of China. Science Press, Beijing, China, 112 pp. Zangerl, R The turtle shell; pp in C. Gans, A. d. A. Bellairs, and T. S. Parsons (eds.), Biology of the Reptilia, Volume 1, Morphology A. Academic Press, New York. Submitted August 13, 2012; revisions received January 7, 2013; accepted January 16, Handling editor: Sean Modesto. APPENDIX 1. Details about characters and taxa added to matrix of Danilov and Syromyatnikova (2009a, 2009b). Character 76 (76) Vertebral 5: wider than more anterior vertebrals (0); narrower than more anterior vertebrals (1). Scorings Xinjiangchelys levensis,?;x. tianshanensis,0;carettochelys insculpta, ;Apalone ferox, ;Yehguia tatsuensis,?; Adocus aksary, 1;A. amtgai, 1;A. beatus/adocus sp., 0; A. bossi, 1; A. inexpectatus, 1; A. kirtlandius, 0; Ferganemys itemirensis, 0; F. verzilini, 0; Shachemys ancestralis, 0; Sh. baibolatica, 0; Sh. laosiana, 0;Kharakhutulia kalandadzei,?;zangerlia testudinimorpha, 0;Z. neimongolensis, 0;Z. ukhaachelys,?;hanbogdemys orientalis, 0;Anomalochelys angulata,?;nanhsiungchelys wuchingensis,?;basilemys variolosa, 0;B. nobilis, 0;B. sinuosa, 0; B. praeclara,?. Character 77 (77) Marginals overlapping onto costals: beginning with marginal 5 (0); beginning with marginal 3 or 4 (1).

11 1080 JOURNAL OF VERTEBRATE PALEONTOLOGY, VOL. 33, NO. 5, 2013 Scorings Xinjiangchelys levensis,?;x. tianshanensis,?;carettochelys insculpta, ; Apalone ferox, ; Yehguia tatsuensis,?; Adocus aksary, 1; A. amtgai, 1; A. beatus/adocus sp., 0; A. bossi, 0;A. inexpectatus, 1;A. kirtlandius, 0; Ferganemys itemirensis, ;F. verzilini, ;Shachemys ancestralis, ;Sh. baibolatica, ;Sh. laosiana, ;Kharakhutulia kalandadzei, ; Zangerlia testudinimorpha, ; Z. neimongolensis, ; Z. ukhaachelys, ;Hanbogdemys orientalis, ;Anomalochelys angulata, ; Nanhsiungchelys wuchingensis, ; Basilemys variolosa, ;B. nobilis, ;B. sinuosa, ;B. praeclara,. Character 78 (78) Shape of the anterior lobe of the plastron: rounded (0); truncated (1). Scorings Xinjiangchelys levensis,0;x. tianshanensis,0;carettochelys insculpta, 0;Apalone ferox, ;Yehguia tatsuensis, 0; Adocus aksary, 1;A. amtgai, 1;A. beatus/adocus sp., 1; A. bossi, 0; A. inexpectatus, 0; A. kirtlandius, 0; Ferganemys itemirensis, 1; F. verzilini, 0; Shachemys ancestralis, 0; Sh. baibolatica, 0; Sh. laosiana, 0;Kharakhutulia kalandadzei, 0;Zangerlia testudinimorpha,?;z. neimongolensis, 0;Z. ukhaachelys, 0;Hanbogdemys orientalis, 0;Anomalochelys angulata,?;nanhsiungchelys wuchingensis, 0;Basilemys variolosa, 0;B. nobilis, 0;B. sinuosa, 0; B. praeclara,0. APPENDIX 2. Characters coded for Adocus amtgai, A. bossi, A. inexpectatus, anda. kirtlandius, and added to the matrix of Danilov and Syromyatnikova (2009a, 2009b). Adocus amtgai ?0???????1? A. bossi??????????????????????????0?00?101000??? ? ? 1001?110 Adocus inexpectatus??????????????????????????0000?10???0?????0?? ?110 A. kirtlandius??????????????????????????0????100000??? 0? ?????001001? 1001?010