Shell characterization of the youngest valid species of the European Eocene genus Neochelys (Pleurodira, Podocnemididae): The Spanish Bartonian Neochelys salmanticensis.

The freshwater pleurodiran turtle Neochelys is the best-represented member of Podocnemididae in the European record, being known by eight Eocene species. The youngest of them is the Bartonian (middle Eocene) Neochelys salmanticensis, from the Duero Basin (Salamanca Province, Central Spain). It corresponds to the largest representative known for this genus, its shell reaching 50 cm in length. Despite this form was defined several decades ago, the information currently available on it is very limited, being restricted to shell remains of less than 10 individuals. In fact, this species lacks a valid diagnosis, considering the current knowledge about the genus. Numerous remains (i.e., more than 1,200) of the shell of this Spanish species are identified. Its detailed study is presented here, so that the anatomy of its shell is characterized in detail. In addition, several aspects related to its intraspecific variability are analyzed, relative to the individual, ontogenetic, and sexual variability. In this way, the shell of N. salmanticensis can be characterized with greater precision than that of any other species of the genus.