Kalasinemys, a new xinjiangchelyid turtle from the Late Jurassic of NE Thailand

Abstract

A new xinjiangchelyid turtle, Kalasinemys prasarttongosothi n. gen. n. sp., is described on the basis of skull and shell material from the Upper Jurassic Phu Kradung Formation at Phu Noi locality, Kalasin Province, in NE Thailand. This second xinjiangchelyid turtle from Phu Noi is distinct from Phunoichelys thirakhupti by the smooth shell surface, the presence of a cervical notch, and vertebral 1 narrower than nuchal. The skull presents an arterial system characteristic of the Xinjiangchelyidae (basal Eucryptodira), and its outline is similar to that of Annemys spp. known from the Middle-Late Jurassic of China and Mongolia, but distinct from the latter mainly by the wider triturating surface, smaller foramen palatinum posterius and the shape of the prefrontal and frontal, as well as that of the basisphenoid and basioccipital. Based on the turtle assemblages, the correlation with mainland Asia further supports a Late Jurassic age for the lower part of the Phu Kradung Formation where Phu Noi site is located stratigraphically. Our study provides new insight on the evolution of the basal eucryptodiran turtles in Asia.