New Insights into the Origin and Phylogeny of Cryptodiran Turtles Based on Key Fossil Taxa from the Mesozoic of Asia

Most turtles from the Jurassic to Early Cretaceous of Asia are referred to the poorly circumscribed taxa Xinjiangchelyidae, Sinemydidae, and Macrobaenidae, groups that mostly include shell-based, generalized, small to mid-sized aquatic forms that are widely considered to represent the stem lineage of Cryptodira. These groups are critical for reconstructing the plesiomorphic anatomy of crown-cryptodires, the most diverse group of living turtles, and they are therefore particularly relevant for understanding the origin and early divergence of the primary clades of extant turtles. The complete description of excellent xinjiangchelyid and sinemydid material from the Upper Jurassic of Mongolia and the Middle Jurassic and Early Cretaceous of China (referable to Annemys levensis, A. latiens, Xinjiangchelys wusu nov. sp. and Manchurochelys manchoukuoensis) provides new insights into the anatomy of these otherwise poorly known groups. The overall similarity of the shells of the two Annemys species combined with significant differences in the skull indicate that these turtles probably partitioned the aquatic niche by exploring different feeding strategies. Among xinjiangchelyids, at least three different skull morphotypes can be differentiated, which implies a moderate level of ecological diversification among Late Jurassic Asian turtles. Phylogenetic definitions of Xinjiangchelyidae, Sinemydidae, and Macrobaenidae are provided for nomenclatural clarity and precision. Phylogenetic analysis weakly supports the inclusion of Xinjiangchelys wusu n. sp., A. levensis, and A. latiens in a monophyletic polytomy with other xinjiangchelyids, including Xinjiangchelys junggarensis and X. radiplicatoides. However, the analysis supports the unorthodox, though tentative placement of xinjiangchelyids and sinemydids outside of crown-group Testudines. A particularly interesting new observation is that the skull of xinjiangchelyids retains such primitive features as a reduced interpterygoid vacuity and basipterygoid processes. The homology of the basipterygoid processes is confidently demonstrated based on a comprehensive review of the basicranial anatomy of Mesozoic turtles and a new nomenclatural system is introduced for the carotid canal system of turtles. The loss of the basipterygoid process and the bony enclosure of the carotid circulation system occurred a number of times independently during turtle evolution suggesting that the reinforcement of the basicranial region was essential for developing a rigid skull, thus paralleling the evolution of other amniote groups with massive skulls. A thorough revision of the phylogeny of Macrobaenidae, Sinemydidae, and closely allied forms yielded two main competing hypotheses: in the first, these taxa form a paraphyletic grade, whereas in the second they form a monophyletic clade. The inclusion of problematic tree changing taxa, such as Panpleurodires (stem + crown side-neck turtles) has a major influence on the phylogenetic relationships of Sinemydidae and closely allied forms. Manchurochelys manchoukuoensis nests within Sinemydidae together with Sinemys spp. and Dracochelys bicuspis in the majority of the analyses

An enigmatic crocodyliform tooth from the bauxites of western Hungary suggests hidden mesoeucrocodylian diversity in the Early Cretaceous European archipelago

Background. The Cretaceous of southern Europe was characterized by an archipelago setting with faunas of mixed composition of endemic, Laurasian and Gondwanan elements. However, little is known about the relative timing of these faunal influences. The Lower Cretaceous of East-Central Europe holds a great promise for understanding the biogeographic history of Cretaceous European biotas because of the former proximity of the area to Gondwana (as part of the Apulian microcontinent). However, East-Central European vertebrates are typically poorly known from this time period. Here, we report on a ziphodont crocodyliform tooth discovered in the Lower Cretaceous (Albian) Alsopere Bauxite Formation of Olaszfalu, western Hungary. Methods. The morphology of the tooth is described and compared with that of other similar Cretaceous crocodyliforms. Results. Based on the triangular, slightly distally curved, constricted and labiolingually flattened crown, the small, subequal-sized true serrations on the carinae mesially and distally, the longitudinal fluting labially, and the extended shelves along the carinae lingually the tooth is most similar to some peirosaurid, non-baurusuchian sebecosuchian, and uruguaysuchid notosuchians. In addition, the paralligatorid Wannchampsus also possesses similar anterior teeth, thus the Hungarian tooth is referred here to Mesoeucrocodylia indet. Discussion. Supposing a notosuchian affinity, this tooth is the earliest occurrence of the group in Europe and one of the earliest in Laurasia. In case of a paralligatorid relationship the Hungarian tooth would represent their first European record, further expanding their cosmopolitan distribution. In any case, the ziphodont tooth from the Albian bauxite deposit of western Hungary belongs to a group still unknown from the Early Cretaceous European archipelago and therefore implies a hidden diversity of crocodyliforms in the area

A preliminary report on the Late Oligocene vertebrate fauna from Máriahalom, Hungary

Relatively sparsely found fossil vertebrate remains have been collected with variable intensity from the Upper Oligocene sand beds of Máriahalom during the last twenty-five years. Recent fieldworks and the obtaining of a private collection have provided good opportunity for a preliminary study of this diverse fauna for the first time. Currently hundreds of isolated specimens are housed at the Natural History Museum of the Eötvös University and so far 26 different taxa have been determined. The Máriahalom fauna consists of both shallow marine and terrestrial elements as demonstrated by the remains of various shark genera, myliobatoid rays, bony fishes, turtles, an anguid squamate, crocodylians, birds, anthracotheriid and ruminant artiodactyls and primitive ursid and mustelid carnivorans. The various habitat preferences of these forms and the accumulation of their remains in the same beds might reflect a transportation process by intense sea currents which is consistent with the sedimentological interpretation of the strata. Apparently Máriahalom is a significant vertebrate site, as Late Oligocene reptiles, birds and large terrestrial mammals have been extremely poorly known from eastern Europe. Concerning the mammals, Máriahalom shows considerable affinities with Late Oligocene faunas in Western Europe

Vertebrate remains from the Upper Cretaceous (Santonian) Ajka Coal Formation, western Hungary

Vertebrate remains from the Upper Cretaceous (Santonian) Ajka Coal Formation (Bakony Mountains, western Hungary) are described. Macro- and microfossils collected from two boreholes and from isolated chunks of sediment/matrix dumped on spoil heaps of the Jókai Mine represent pycnodontiform and lepisosteiform fishes, bothremydid turtles, the mosasauroid Pannoniasaurus inexpectatus, the crocodyliforms cf. Theriosuchus, Iharkutosuchus makadii and cf. Allodaposuchus, as well as ankylosaurian and theropod dinosaurs. This unit was deposited in a swampy lacustrine environment, in contrast with the neighbouring and contemporaneous floodplain deposit of the vertebrate-bearing Csehbánya Formation at Iharkút. Despite significant environmental differences, the faunal composition of the Ajka Coal Formation assemblage completely overlaps with that of the Csehbánya Formation, suggesting the occurrence of the same semi-aquatic and terrestrial species in both settings. The ankylosaurian remains further strengthen the previous view that ankylosaurus preferred wetland habitats such as fluvial systems and coastal regions. © 2015 Elsevier Ltd

A new xinjiangchelyid turtle from the Middle Jurassic of Xinjiang, China and the evolution of the basipterygoid process in Mesozoic turtles

Background: Most turtles from the Middle and Late Jurassic of Asia are referred to the newly defined clade Xinjiangchelyidae, a group of mostly shell-based, generalized, small to mid-sized aquatic froms that are widely considered to represent the stem lineage of Cryptodira. Xinjiangchelyids provide us with great insights into the plesiomorphic anatomy of crown-cryptodires, the most diverse group of living turtles, and they are particularly relevant for understanding the origin and early divergence of the primary clades of extant turtles. Results: Exceptionally complete new xinjiangchelyid material from the ?Qigu Formation of the Turpan Basin (Xinjiang Autonomous Province, China) provides new insights into the anatomy of this group and is assigned to Xinjiangchelys wusu n. sp. A phylogenetic analysis places Xinjiangchelys wusu n. sp. in a monophyletic polytomy with other xinjiangchelyids, including Xinjiangchelys junggarensis, X. radiplicatoides, X. levensis and X. latiens. However, the analysis supports the unorthodox, though tentative placement of xinjiangchelyids and sinemydids outside of crown-group Testudines. A particularly interesting new observation is that the skull of this xinjiangchelyid retains such primitive features as a reduced interpterygoid vacuity and basipterygoid processes. Conclusions: The homology of basipterygoid processes is confidently demonstrated based on a comprehensive review of the basicranial anatomy of Mesozoic turtles and a new nomenclatural system is introduced for the carotid canal system of turtles. The loss of the basipterygoid process and the bony enclosure of the carotid circulation system occurred a number of times independently during turtle evolution suggesting that the reinforcement of the basicranial region was essential for developing a rigid skull, thus paralleling the evolution of other amniote groups with massive skulls. © 2013 Rabi et al.; licensee BioMed Central Ltd

A new alligatoroid from the Eocene of Vietnam highlights an extinct Asian clade independent from extant Alligator sinensis

During systematic paleontological surveys in the Na Duong Basin in North Vietnam between 2009 and 2012, well-preserved fossilized cranial and postcranial remains belonging to at least 29 individuals of a middle to late Eocene (late Bartonian to Priabonian age (39–35 Ma)) alligatoroid were collected. Comparative anatomical study of the material warrants the diagnosis of a new taxon, Orientalosuchus naduongensis gen. et sp. nov. The combined presence of an enlarged fifth maxillary tooth, prominent preorbital ridges, a large supraoccipital exposure on the skull table, a palatine-pterygoid suture anterior to the posterior end of the suborbital fenestra, and a pterygoid forming a neck surrounding the choana is unique to this species. Unlike previous phylogenies, our parsimony analysis recovers a monophyletic Late Cretaceous to Paleogene East to Southeastern Asian alligatoroid group, here named Orientalosuchina. The group includes Orientalosuchus naduongensis, Krabisuchus siamogallicus, Eoalligator chunyii, Jiangxisuchus nankangensis and Protoalligator huiningensis, all of them sharing a medial shifted quadrate foramen aerum. The recognition of this clade indicates at least two separate dispersal events from North America to Asia: one during the Late Cretaceous by Orientalosuchina and one by the ancestor of Alligator sinensis during the Paleogene or Neogene, the timing of which is poorly constrained