Otwayemys, a new cryptodiran turtle from the early Cretaceous of Australia. American Museum novitates ; no. 3233

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New York, NY : American Museum of Natural History
"The Early Cretaceous Eumeralla Formation, Otway Group, of Cape Otway, Victoria, Australia, has yielded remains of a new genus of eucryptodiran turtle, Otwayemys cunicularius, n. gen., n. sp. Otwayemys is based primarily on shell material, but unassociated skull elements, cervical and caudal vertebrae, and limb elements from the type locality are attributed to this taxon. Otwayemys cunicularius is characterized by a carapace with an emarginate nuchal area, wide vertebral scales, and a smooth shell texture; and by a plastron with wide epiplastra, small extragular scales (scale set 2), gular scales (scale set 1) extending onto entoplastron, a small and narrow entoplastron, a large hyoplastron/hypoplastron fontanelle, and an inguinal buttress terminating on the sixth peripheral. The shell of Otwayemys is most similar to Xinjiangchelys from the Jurassic of China; both have broad epiplastra, plastral buttresses not extending onto costals, a long first thoracic rib, no inclination to the first thoracic centrum, and no mesoplastra; all these characters are primitive for the Eucryptodira. Otwayemys is advanced over Xinjiangchelys in having formed vertebral articulations in the neck. Biconvex eighth and biconcave fifth (?) cervicals in Otwayemys are characters found in the Early Cretaceous Ordosemys of central Asia. Otwayemys differs from Chelycarapookus, also from the Early Cretaceous of Victoria, in being 20% larger and having a large plastral fontanelle, a smooth surface texture, and a wide posterior plastral lobe. Otwayemys belongs in the Centrocryptodira, eucryptodires with formed vertebral articulations. A parsimony analysis of 18 taxa using 40 characters (of which only 20 are known for Otwayemys) produces 12 equally parsimonious trees. A consensus tree shows Otwayemys and Meiolaniidae in an unresolved trichotomy with Polycryptodira (consisting primarily of the living cryptodires) plus Sinemydidae"--P. [1].
28 p. : ill. ; 26 cm.
Includes bibliographical references (p. 39-40).