First authentic record of the freshwater turtle Mauremys from the Upper Pliocene of Italy, with a new occurrence of the rarely reported ichnotaxon Thatchtelithichnus holmani

Abstract

Nowadays, the living species of the terrapin genus Mauremys (Testudinoidea: Geoemydidae) are mostly found in eastern Asia, but three of them inhabit the Western Palearctic ecozone. In Italy, occurrences of living individuals of Mauremys are interpreted as records of alien species; however, a growing fossil record demonstrates that this genus has inhabited Italy as recently as the Late Pleistocene. We report on a new fossil specimen of Mauremys from the Upper Pliocene (Piacenzian) marginal-marine deposits of Tuscany (central Italy). This find, consisting of a partial plastron and a loose neural, represents the second authentic report of Mauremys from the Italian Pliocene, as well as the first one from the Piacenzian of Italy. Therefore, it is a significant fossil that fills a gap in the chronostratigraphic distribution of Italian fossil Mauremys, helping – together with the Lower Pliocene holotype of Mauremys portisi – to bridge the rich Miocene and Pleistocene segments of this record. Moreover, two unusual scars observed on the external surface of the studied plastron are here referred to the ichnospecies Thatchtelithichnus holmani. These traces represent one of the few records worldwide of this rarely identified ichnospecies, as well as its geologically youngest published occurrence. Hypotheses regarding the origin of the Thatchtelithichnus traces are reevaluated, and an origin as attachment scars of aquatic ectoparasites (possibly ticks, leeches, or flukes) is reaffirmed as probable in cases of traces occurring on the exterior of the plastral bones of turtles.