A new bothremydid turtle (Pleurodira) from the Upper Cretaceous (Cenomanian) of Madagascar

Abstract

The find of a partial shell of a pleurodiran turtle from the Cenomanian (basal Upper Cretaceous) of Madagascar was reported in the 1980s. It was then referred to as a potential member of the bothremydid Bothremys, but it has remained unpublished until now. Its attribution to Bothremydidae is confirmed here, since it is identified as a representative of Bothremydina, a clade known by several freshwater to littoral species from North America, southwestern Europe, northern Africa and the Middle East. The turtle from Madagascar, showing several exclusive characters within this lineage, is attributed to a new littoral form, Akoranemys madagasika gen. et sp. nov. It corresponds to one of the few Mesozoic turtle taxa defined in Madagascar, where only two pleurodires, belonging to other clades (the bothremydid Kurmademydini and the non-bothremydid Euraxemydidae), had been recognized at a specific level, both species being exclusive to the Maastrichtian record of that country. Therefore, Akoranemys madagasika corresponds to the oldest turtle defined for the fossil record of Madagascar, but also to one of the oldest known members of Bothremydina worldwide. The analyzed specimen is the only Mesozoic fossil turtle so far identified in the southwestern area of Madagascar, all other remains from that country coming from the northwestern region. Therefore, the presence of Bothremydina in Madagascar is confirmed by this unique member defined for the Southern Hemisphere, and the palaeobiogeographic distribution of this lineage is remarkably expanded.