New Material and a Reassessment of Soft-Shelled Turtles (Trionychidae) from the Late Cretaceous of Middle Asia and Kazakhstan

摘要

In this paper we describe previously unpublished trionychid turtle material, consisting of numerous shell fragments, from two Late Cretaceous (Santonian-early Campanian) localities from Middle Asia and Kazakhstan (Central Asia in the U.S. tradition): Kansai (Tadjikistan) and Shakh-Shakh (Kazakhstan). This material can be attributed to two forms of trionychids present in both localities. One of them is the named species Trionyx riabinini Kuznetsov and Chkhikvadze, 1987, described from Shakh-Shakh. New data on its shell morphology provided by our study allow attribution to the genus Aspideretoides Gardner et al., 1995, known previously only from the Campanian-Maastrichtian of North America. The presence of this taxon in both Middle Asia and North America provides the first clear evidence for the relationship between Cretaceous Asian and North American trionychids. The second form is established as a new species, oTrionyxo kansaiensis, sp. nov., with unclear systematic position within Trionychinae. We lastly present a brief review of other named taxa of Cretaceous trionychids of Middle Asia and Kazakhstan.