Collaborative Investigation of Earliest Crayfish: Paleobiologic, Paleoecologic and Paleoclimatic Implications

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Miller: OPP 9614709 Isbell: OPP 9615045 Babcock: OPP 9614989 Abstract During the 1995-96 Austral summer field season the oldest known fossil crayfish and one of the oldest known occurrences of fossil crayfish burrows were found in the Shackleton Glacier area of Antarctica. This award supports a collaborative, interdisciplinary study to expand on these discoveries. The crayfish claw was found in the Upper Carboniferous to Lower Permian Pagoda Formation deposited in glacial environments 280 to 300 million years ago; the discovery pushes back the first occurrence of crayfish 65 to 75 million years. The crayfish burrows were found in the Lower Triassic Fremouw Formation deposited approximately 240 million years ago. Their abundance and complexity indicate that crayfish developed burrowing behavior early in their long history. The objectives of the study are to collect additional crayfish body and trace fossils from Antarctica, to use these fossils to develop further insight into the depositional conditions in parts of that continent during intervals of the Late Carboniferous- Early Permian and the Early Triassic, and to study the early evolutionary and burrowing history of freshwater astacoid decapods (crayfish). Specifically, the work plan is: 1) to search for more fossil crayfish and crayfish burrows in the Pagoda Formation; 2) to interpret the way of life of the crayfish in the Pagoda Formation and relate it to the crayfish morphology; 3) to reconstruct the depositional environment and paleoclimate recorded by the crayfish-bearing rocks; 4) to search for crayfish within burrows in the Fremouw Formation; 5) to quantitatively describe the burrows in the Fremouw Formation; and 6) to compare the morphology and behavior of Late Carboniferous to Early Permian crayfish and burrows to those of the Early Triassic and later. This study will elucidate the evolutionary and behavioral history of crayfish. Modern crayfish exert an important control on paramet ers such as energy flow, biotic species composition, and biotic abundance in many different aquatic ecosystems. This proposed study will yield information about how and when this environmental and behavioral diversification took place, as well as increase understanding of the late Paleozoic and early Mesozoic paleoclimates.