A basal eucryptodiran turtle 'Sinemys' efremovi [-Waguia efremovi] from the Early Cretaceous of China

A reexamination of the type material (two specimens considered for a long time lost) of the poorly known turtle “Sinemys” efremovi Khosatzky, 1996 from the Early Cretaceous Tugulu Group of northwest China, allows us to present new observations, images, and taxonomic conclusions about these important specimens. We conclude that: (1) “S.” efremovi is referrable to the basal eucryptodire genus Wuguia Matzke, Maisch, Pfretzschner, Sun, and Stöhr, 2004 based on a small size (up to 150 mm in shell length), absence of the nuchal emargination, presence of additional ossifications in the suprapygal region of the carapace and similar plastral proportions with relatively long bridges (35−45% of the plastron width), and a narrow and elongated posterior lobe; (2) “S.” efremovi is a senior subjective synonym of Dracochelys wimani Maisch, Matzke, and Sun, 2003, another species recently described from the Tugulu Group. As construed here, Wuguia includes two species: W. efremovi (Khosatzky, 1996) and W. hutubeiensis Matzke, Maisch, Pfretzschner, Sun, and Stöhr, 2004. New diagnoses for these taxa are given.