Cranial morphology of an Early Cretaceous Monjurosuchid (Reptilia: Diapsida) from Liaoning Province of China and evolution of the choristoderan palate |
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Authors: | Ke-Qin Gao Daniel Ksepka Hou Lianhai Duan Ye Hu Dongyu |
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Institution: | 1. School of Earth and Spaces Sciences, Peking University , Beijing, 100871, People's Republic of China kqgao@pku.edu.cn;3. American Museum of Natural History , Central Park West at 79th Street, New York, NY, 10024, USA;4. Shenyang Normal University , 253 Huanghebei Street, Shenyang, 110034, People's Republic of China |
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Abstract: | A new specimen of Philydrosaurus proseilus from the Early Cretaceous Chiufotang (Jiufotang) Formation preserves the first complete palate of a monjurosuchid choristodere. As in other choristoderes, the palate of Philydrosaurus is akinetic, extended by a broad contact between the vomer and maxilla, and equipped with multiple batteries of palatal teeth. This specimen provides phylogenetically significant information and clarifies the distribution of many apomorphies within Choristodera. Philydrosaurus is primitive relative to the Neochoristodera in that it exhibits only a moderate degree of posterior displacement of the choanae and retains a relatively large interpterygoid vacuity. However, Philydrosaurus also exhibits several derived features previously considered diagnostic of the Neochoristodera, including establishment of a long midline contact of the pterygoids and development of a distinct nasopalatal trough extending from the choana. The choristodere palate exhibits significant modification of the primitive diapsid condition, including elongation of the vomers, establishment of a vomer–maxilla contact, posterior displacement of the choanae, development of the nasopalatal trough, and reduction of the interpterygoid vacuity. |
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Keywords: | Diapsid reptiles Choristodera Early Cretaceous Chiufotang Formation western Liaoning of China evolution of palatal structures |
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