Do Hyeon Kim - Paleobiogeographic review of Early Cretaceous trionychians

SCIMED - Geosciences - Turtle Evolution Symposium 2024

7:48, 1 July, Korean, 1 view

Based on the fossil records from the Lower Cretaceous formations of Japan and SE Asia, it is suggested that the trionychians originated from Asia. They diversified into two groups later, the carettochelyids and pantrionychids. Most carettochelyids occurred in Southeast Asia during the Early Cretaceous, whereas all the pantrionychids were limited to Central and East Asia. It has been suggested that there was a geographical isolation between SE Asia and the mainland during the Neocomian, and this physical barrier may have caused the allopatric speciation among the earliest members of the Pan-Trionychia, corresponding to the common ancestors of the carettochelyids and the pantrionychids. This hypothesis is support by the similar distributional aspects of other turtles during the Early Cretaceous in Asia, including adocids, macrobaenids, sinemydids. The carettochelyid materials from the Lower Cretaceous Tatsukawa and Kitadani formations (Barremian ~ Aptian) of Japan, which represents the only record of Early Cretaceous carettochelyid outside the SE Asia, suggests that the dispersal of carettochelyids were somewhat more flexible than pantrionychids. The most influential factor that made this possible is inferred to be dispersal by marine routes bypassing the physical barrier. However, such inference requires further discussions, since both carettochelyids and pantrionychids are known for having tolerance in saline environments.

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