Article: Turtles all the way down: Neogene pig-nosed turtle fossil from southern Australia reveals cryptic freshwater turtle invasions and extinctions

Abstract The extant pig-nosed turtle (Carettochelys insculpta), persisting in far northern Australia and southern New Guinea, is the last surviving member of Carettochelyidae and the only non-Gondwanan freshwater turtle lineage in Australia. Despite having a global fossil record dating to the Cretaceous, the absence of carettochelyid fossils from Australia has implied a relatively recent colonization of this landmass. Here we report an upper Miocene to lower Pliocene carettochelyid fossil from Beaumaris, Victoria, in south-eastern Australia. This record is the most southerly occurrence of the clade Carettochelyidae. The presence of carettochelyids in southern Australia, and a discontinuous record of trionychids (soft-shell turtles) in the Cenozoic of Queensland, suggests at least two colonizations of Australia by Trionychia, pre-dating the extant pig-nosed turtle. This cryptic southern history of tropical soft-shell and pig-nosed turtles ended before the recent aridification of Australia, leaving the Gondwanan side-necked turtles as the dominant turtle group in Australian freshwater ecosystems. Therefore, this singular fossil reveals a previously unknown shift in the diversity and evolutionary history of freshwater turtles in Australia.