DECAPOD MATERIAL ASSOCIATED WITH ICHTHYOSAUR REMAINS FROM THE SUNDANCE FORMATION OF NATRONA COUNTY, WYOMING

Decapod material is rare from Jurassic rocks in North America. Recent fieldwork has produced new material found associated with an articulated ichthyosaur (UW 24602) preserved in a calcareous concretion collected from the Redwater Shale member of the Sundance Formation. The decapod material appears to be fragmentary bits of cuticle found mixed into burrow fill within the recesses of the ichthyosaur skull and adjacent to vertebrae. The surface of some ribs and vertebrae are covered with borings suggesting that the ichthyosaur carcass was exposed on the sea floor for some time before burial. At least two generations of cementation been identified in the concretion; both with burrows occurring close to the bone. Calcareous concretions are a common mode of preservation of vertebrates in the Redwater Shale. The discovery of decapod remains associated with a marine reptile suggest a previously untapped potential for collecting new material.