Abstract
A number of helochelydrid turtle shell remains were recovered over the course of the 19th century from mid-Cretaceous sediments throughout Southern England, including the poorly figured and described types of Trachydermochelys phlyctaenus from the Cambridge Greensand of Cambridgeshire, Plastremys lata from the Upper Greensand of the Isle of Wight, and "Trachydermochelys" rutteri from the Melbury Sandstone of Dorset. A review of stratigraphic provenience suggests that all material originates from late Late Aptian portions of the Upper Greensand or early Early Cenomanian portions of the West Melbury Marly Chalk Formation, a relatively narrow time window geologically speaking. As described, Trachydermochelys phlyctaenus is a problematic taxon, because the most plausible type series is a chimera that includes two helochelydrid morphotypes in addition to protostegid remains. This conundrum is resolved through the designation of a lectotype. A review of all historic material confirms the presence of three English taxa distinct from Helochelydra danubina, a coeval taxon named from Germany. At least four helochelydrid taxa, therefore, occurred in western Europe during the Early to Late Cretaceous transition.