Manchurochelys manchoukuoensis is a sinemydid stem-cryptodire turtle known by fossils
from the Lower Cretaceous beds exposed in western Liaoning and Inner Mongolia of China.
This fossil taxon is important for understanding the origin and evolution of Cryptodira
(crown-group hidden-neck turtles). The holotype of M. manchoukuoensis was presumably
lost during the Second World War and several aspects of the osteology of the species
remains unknown. We here describe a near-complete fossil skeleton coming from the
Lower Cretaceous Yixian Formation, western Liaoning, China, 50 km away from the type
locality in the same formation. PKUP V1071 represents the most completely preserved
specimen of the species and includes a well-preserved plastron, which was otherwise
only known partially in the lost holotype. We provide a detailed osteological description
of M. manchoukuoensis including data from micro-CT and X-ray computed laminography
scanning of PKUP V1071. Of particular significance is the anchor-shaped entoplastron
transversely extending to completely separate the small and triangular epiplastra
from the hyoplastra; this peculiar morphology is otherwise only present in Sinemys
spp. among turtles. Additional novel insights into plastron and cranial anatomy further
support a close relationship between Sinemys and Manchurochelys.
