Fossil evidence in Australia for oldest known freshwater crayfish of Gondwana

Early Cretaceous body and trace fossils in Victoria, Australia, establish the oldest known presence of parastacid crayfish (Decapoda: Astacidea, Parastacoidea) in freshwater environments of Australia, and the oldest known crayfish in Gondwana. Parastacid body fossils, comprised of a partial abdomen (Palaeoechinastacus australianus, gen. et sp. nov.) and two chelae, are from a fluvial deposit in the Otway Group (Albian). Trace fossils in fluvial deposits of the Otway Group and Strzelecki Group (Aptian) also closely resemble modern parastacid burrow systems, supplying independent verification of crayfish presence and their burrowing habits in Australia at this time. Paleoenvironments in this region were high-latitude and periglacial, indicating that these crayfish were adapted to cold-water ecosystems. The combined fossil evidence provides a starting point for the previously unknown paleoecology and evolutionary history of Mesozoic parastacids in Australia, while supporting phylogenies that suggest parastacid radiation from southeastern Australia before the complete breakup of Gondwana.