Where is the Fossil Evidence for Gondwanan Crayfish?

Abstract

Crayfish body- and ichnofossils recently reported from Lower Permian and Lower Triassic strata of Antarctica have been reinterpreted to be the body fossils of euthycarcinoid arthropods and the burrows of small- to large-sized therapsids (mammal-like reptiles). The earliest fossil evidence of crayfish presence and activity in continental deposits is still from the Laurasian continents of Pangea. This evidence is in the form of body fossils and burrows from the Upper Triassic and burrows from the Lower Permian of the American southwest. For that matter, nearly all ichno- and body fossils have been described from Laurasian rocks with the exception of the occurrence of an isolated claw of a parastacid crayfish from Paleogene deposits in Queensland, Australia. Where is all the fossil evidence for Gondwanan crayfish? There is a rich extant diversity of parastacid crayfish in Australia, and they are dispersed between other Gondwanan continents, with the exception of Africa and Antarctica. Paleontological and ichnological evidence, when taken into consideration with paleogeographic reconstructions, indicates that they originated early, during, or slightly after the formation of Pangea. Thus, at the very least, there should be trace and body fossil evidence in Australia indicating the long evolutionary history of the parastacids. Evidence for ancient Gondwanan crayfish in terrestrial and freshwater ecosystems should occur in rocks of similar ages to those in North America where ichno- and body fossils have been identified.