Cretaceous Research 49 (2014) 1e12 Contents lists available at ScienceDirect Cretaceous Research journal homepage: www.elsevier.com/locate/CretRes Soft-shelled turtles (Trionychidae) from the Cenomanian of Uzbekistan Natasha S. Vitek b, Igor G. Danilov a,* a Jackson School of Geosciences, The University of Texas at Austin, Austin, TX, USA b Zoological Institute of the Russian Academy of Sciences, Universitetskaya Emb. 1, 199034 St. Petersburg, Russia article info abstract Article history: Localities from the Cenomanian of Uzbekistan are the oldest in Middle Asia and Kazakhstan to preserve Received 14 June 2013 two broadly sympatric species of trionychid turtle. Material described here comes from multiple Cen- Accepted in revised form 11 January 2014 omanian formations from the Itemir locality, and from multiple localities in the Cenomanian Khodzhakul Available online 22 February 2014 Formation. The first taxon from the locality, “Trionyx” cf. kyrgyzensis, has multiple morphological simi- larities with the older, Early Cretaceous “Trionyx” kyrgyzensis. In contrast, the second taxon, “Trionyx” Keywords: dissolutus, has multiple similarities with “Trionyx” kansaiensis, one of two species of trionychid found in Turtles younger Late Cretaceous localities. “Trionyx” dissolutus bears some superficial resemblance to other tri- Testudines fi Trionychidae onychid taxa within the clade Plastomenidae because of its highly ossi ed plastron with a hyoplastral Assemblage lappet and an epiplastral notch. However, Plastomenidae is diagnosed primarily through characters that Cretaceous are absent or cannot be observed in the available material of “T.” dissolutus, and other shared features are Middle Asia plesiomorphic. In addition, “T.” dissolutus shares other synapomorphies with Trionychinae. A heavily Kazakhstan ossified plastron may be more homoplastric within Trionychidae than has been previously recognized. Finally, we provide an improved understanding of the subtle similarities and differences between several closely related Cretaceous turtle assemblages of Middle Asia and Kazakhstan. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Karakalpakistan, and from the Cenomanian of the Itemir locality in the central Kizylkum Desert, Navoi Viloyat (district) (Fig. 1). The Trionychidae Gray 1825, or soft-shelled turtles, are a group of localities of the Khodzhakul Formation include Chelpyk (SCH-1 and aquatic cryptodires (Meylan,1987). The phylogeny and taxonomy of SCH-“B” sites), Khodzhakul I (SKH-20 site), Khodzhakulsai (SKH-4, extinct species within this group are still not well understood SKH-5, and SKH-25 sites), and Sheikhdzheili (SSHD-8 and SSHD-8a (Meylan, 1987; Gardner et al., 1995; Karl, 1998; Joyce and Lyson, sites) (see Averianov and Archibald [2005] for more details about 2011). The lack of understanding is especially problematic for the localities of the Khodzhakul Formation). In addition, one more Cretaceous trionychids, which are important for understanding the locality known as Khodzhakul II (SKH-26 site) contains Cen- early diversification and evolution of the family (Danilov and Vitek, omanian remains from the Khodzhakul Formation which were 2012 provided a review of Cretaceous trionychids of Asia). redeposited in Late Paleocene sands (Nessov, 1997). The described This paper continues a series of publications on Cretaceous tri- material from Itemir comes from several Cenomanian members onychids of Asia (Danilov and Vitek, 2009; Vitek and Danilov, 2010, (formations) of the following sites: CDZH-3, CDZH-5b, CDZH-10, 2012, 2013; Danilov and Vitek, 2012, 2013) and is devoted to tri- CDZH-12 and IT-1 (see Nessov (1997) and Averianov and Sues onychids from the early Late Cretaceous (Cenomanian) of Uzbeki- (2007) for more details about the Itemir locality). stan, situated in the region called Middle Asia and Kazakhstan Trionychid material from the Khodzhakul Formation was (Fig. 1; see Vitek and Danilov [2010] for more details about the mentioned in the literature (Nessov, 1977a, 1985, 1986; Kordikova, geography of Middle Asia and Kazakhstan). The material described 1992, 1994; Nessov, 1997), but was never described. The trionychid in this paper comes from localities in the early Cenomanian material from the Itemir locality was mentioned and partially Khodzhakul Formation of the southwestern Kizylkum Desert area, illustrated (Nessov, 1984, 1985; Kordikova, 1992, 1994; Nessov, 1997; Danilov and Vitek, 2009, 2012). The trionychid material described in this paper consists of * Corresponding author. numerous shell fragments. It is assigned to two shell-based taxa, E-mail address: [email protected] (I.G. Danilov). “Trionyx” cf. kyrgyzensis Nessov, 1995 and “Trionyx” dissolutus sp. 0195-6671/$ e see front matter Ó 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.cretres.2014.01.004 2 N.S. Vitek, I.G. Danilov / Cretaceous Research 49 (2014) 1e12 Fig. 1. Map showing main localities of Cretaceous trionychids in Middle Asia and Kazakhstan. A e Dzharakuduk; B e Baybishe; C e Shakh Shakh; D e Kyrkkuduk I; E e Kansai; F e Kylodzhun; G e localities of the Khodzhakul Formation (see Vitek and Danilov (2010, 2012, 2013) and Danilov and Vitek (2013) for data on localities other than localities of the Khodzhakul Formation and Itemir). nov. Material that cannot be confidently attributed to these two 8a), partial costal 7?; ZIN PH 5/122 (SSHD-8), partial costal 8; ZIN taxa is considered Trionychidae indet. PH 11/122 (SKH-4), partial costal 8?; ZIN PH 10/122 (SSHD-8a), The material for this study was collected by L.A. Nessov between partial costal; ZIN PH 16/122 (SKH-25), ZIN PH 17/122 (SKH-25), 1977 and 1994 and by the international Uzbek/Russian/British/ ZIN PH 23/122 (SKH-25), ZIN PH 24/122 (SKH-25), partial American/Canadian Joint Paleontological Expeditions (URBAC) led hyoplastra; ZIN PH 18/122 (SSHD-8a), ZIN PH 20/122 (SKH-25), ZIN by J.D. Archibald between 1997 and 2006. PH 21/122 (SKH-25), ZIN PH 22/122 (SKH-25), partial hypoplastra; Anatomical terminology follows Meylan (1987), Gardner and ZIN PH 58/122 (SKH-25), ZIN PH 59/122 (SCH-1), partial xiphi- Russell (1994), and Karl (1999). plastra; Itemir locality: ZIN PH 56/86 (CDZH-5b), partial nuchal; Institutional Abbreviations e ZIN PH, Paleoherpetological ZIN PH 57/86 (IT-1), costal 8; ZIN PH 54/86 (CDZH-12), ZIN PH collection, Zoological Institute of the Russian Academy of Sciences, 55/86 (CDZH-12), external impressions of partial costals 7 and 8. St. Petersburg, Russia. Locality, Horizon, and Age. Chelpyk, Khodzhakul I and II, Khodzhakulsai, and Sheikhdzheili localities, southwestern 2. Systematic paleontology Kizylkum Desert area, Karakalpakistan, Uzbekistan; Khodzhakul Formation, early Cenomanian. Itemir locality, Central Kizylkum Testudines Batsch, 1788 Desert, Navoi Viloyat (district), Uzbekistan; Cenomanian. Cryptodira Cope, 1868 Trionychidae Gray, 1825 Description of material from the Khodzhakul Formation. Shell.A Trionychinae Gray, 1825 reconstruction (Fig. 2A), based on the largest nuchal fragment (ZIN PH 2/122; Fig. 3A), is approximately 30 cm long. A smaller Trionychinae incertae sedis partial nuchal (ZIN PH 3/122; Fig. 3B) with a callosity restricted to “Trionyx” cf. kyrgyzensis Nessov, 1995 the posteromedial part of the bone comes from an individual, Referred material. Khodzhakul Formation: ZIN PH 1/122 (SSHD-8a), likely a juvenile, only about 15 cm long (Fig. 2B). Carapace shape ZIN PH 2/122 (SKH-4), ZIN PH 3/122 (SKH-26), ZIN PH 27/122 was probably oval, but without complete costals 2e7itis (SSHD-8a), ZIN PH 30/122 (SKH-20), partial nuchals; ZIN PH 15/122 impossible to say for certain. It is possible that the carapace was (SSHD-8), hexagonal neural; ZIN PH 69/122 (SSHD-8), tetragonal more circular. The anterior and posterior margins are both neural; ZIN PH 14/122 (SKH-20), pentagonal neural; ZIN PH 6/122 broadly convex, following the terminology of Gardner and Russell (SSHD-8), partial costal 1; ZIN PH 7/122 (SSHD-8a), partial costal (1994). The lateral margin is weakly scalloped. It is unclear 2?; ZIN PH 37/122 (SSHD-8a), partial costal 5; ZIN PH 9/122 (SSHD- whether or not this species was sexually dimorphic. Sculpturing N.S. Vitek, I.G. Danilov / Cretaceous Research 49 (2014) 1e12 3 Fig. 2. Reconstructions of shells of trionychids from the Khodzhakul Formation and Itemir. A, adult carapace; B, juvenile carapace; C, plastron of “Trionyx” cf. kyrgyzensis. D, adult carapace; E, juvenile carapace; F, adult plastron; G, juvenile plastron of “Trionyx” dissolutus sp. nov. is a pattern of wide, irregularly shaped pits. In smaller preserved nuchals (Danilov and Vitek, 2012), but contrary to the specimens, the ridges surrounding the pits are thinner and hypothesized ancestral state for trionychids (Meylan, 1987). The more pronounced, similar to the sculpturing seen in “T.” kyrgy- extent of the sculptured callosity across the plate varies with size. zensis Nessov, 1995. In general, this sculpturing is more similar to Smaller nuchals (ZIN PH 3/122, ZIN PH 27/122; Fig. 3C) have a that of Aspideretoides riabinini (Kuznetsov and Chkhikvadze, smaller callosified area than larger nuchals (ZIN PH 1/122; 1987), than to that of “Trionyx” kansaiensis Vitek and Danilov, Fig. 3D), which in turn have a smaller callosified area than the 2010 (see Vitek and Danilov, 2010; Danilov et al., in press). largest nuchals (ZIN PH 2/122). In general, the nuchals are well- Nuchal. Available nuchal fragments do not preserve the medial sutured to the first costals (ZIN PH 1/122) with a relatively part of the nuchal. Therefore, it is unknown where the first straight suture between the two plates. A few millimeters of the thoracic vertebra contacted the nuchal. The costiform processes posterior margin may lie inside the first costals. Only one small, are united, in contrast to the divided processes of cyclanorbines. presumably juvenile specimen (ZIN PH 30/122; Fig. 3E) has A rough estimate based on two different nuchals (ZIN PH 1/122 postnuchal fontanelles. and ZIN PH 3/122) is that the nuchals were 4.5e5timeswider Neurals. No preneurals or neurals 1 could be assigned to this than long, similar to all Asian Cretaceous trionychids with species.