PALEOZOIC-MESOZOIC CRAYFISH FROM ANTARCTICA - EARLIEST EVIDENCE OF FRESH-WATER DECAPOD CRUSTACEANS

Discovery of an Early Permian claw from Antarctica extends the fossil record of crayfish by similar to 65 m.y. and demonstrates that decapod crustaceans had radiated into freshwater habitats by the late Paleozo ic Burrows in Lower Triassic rocks of Antarctica are among the oldest apparently constructed by crayfish. Their morphology is similar to mod ern crayfish burrows, and this demonstrates that burrowing behavior wa s established early in the evolution of this group. The new discoverie s show that the earliest Permian crayfish were distributed in high pal eolatitudes of southernmost Pangea, where they lived in freshwater lak es fed by glacial meltwater. Modern crayfish habitat, used as a guide to crayfish temperature tolerance, indicates that summer temperatures of streams and lakes mar the South Pole that supported the crayfish pr obably reached 10-20 degrees C during Permian-Triassic interglacial in tervals.