Taphonomic Features of a Lower Permian Beached Cephalopod Assemblage from Central Texas

Abstract

Abstract A taphonomic investigation of a fossil assemblage near Coleman, Texas, U.S.A., has revealed a rarely seen part of the cephalopod taphonomic pathway. The cephalopods occur in a brown shale with a low-diversity, gastropod-dominated fauna that is mixed together with a conifer-seed fern-dominated terrestrial flora. All of the cephalopod shells (n=2000+) are damaged. The brown shale is interpreted as representing a brackish-water or quiet, muddy beach environment, based in part on the delicate three-dimensional preservation of the terrestrial plant debris and the absence of stenohaline benthic marine fauna. Most upper Paleozoic cephalopods (especially ammonoids) are thought to have lived in offshore (middle to outer shelf) environments. The environmental interpretation and the massive damage observed on the cephalopod shells support the interpretation that this cephalopod fauna has been transported from one or more distant offshore biotopes. These cephalopods had shells with positively buoyant conchs ...