A redescription of Elkemys australis (Yeh, 1974), a poorly known basal testudinoid turtle from the Paleocene of China

Abstract

In this study we provide a redescription of the type series of Elkemys australis, a poorly known basal testudinoid turtle (‘Lindholmemydidae’) from the Paleocene of China. Based on new observations we report on some previously overlooked shell characters of Elkemys australis, and also provide a new diagnosis and a new reconstruction for this species. Among ‘lindholmemydids’, Elkemys australis is most similar to Gravemys barsboldi from the Late Cretaceous of Mongolia. Elkemys australis, Gravemys spp. and Hokouchelys chenshuensis from the Paleocene of China differ from other ‘lindholmemydids’ and testudinoids in general in an unique inframarginal pattern (four or five pairs of wide inframarginal scutes which strongly extend on to peripherals), and may form a natural group (either a clade or a grade) of basal testudinoids. Some other characters shared by E. australis, G. barsboldi and H. chenshuensis (large anal notch and relatively narrow vertebrals 2 and 3) are characteristic of some geoemydids and testudinids, that may indicate closer relations of the three mentioned genera to these groups.