BIOMARKERS IN COLORED FOSSIL CRINOIDS: IMPLICATIONS FOR PHYLOGENY

Forty species of crinoids were uncovered in LeGrand, Iowa and fossils from this site became famous for their excellent preservation and peculiar species-specific coloration. Similar trends in color occur among crinoids from the Borden Group (Mississippian) of Indiana, as well as other locations across North America and Europe. Inorganic pigments are usually the cause of unusual coloration in fossils, but in this case the species-specific coloration is due to organic molecules and is not entirely due to taphonomic processes. Biomarker molecules are preserved and have been extracted from some Mississippian and Jurassic crinoids.

Fossil crinoids possess chromophoric, i.e. light absorbing, organic molecules, such as polynuclear aromatic hydrocarbon quinones that resist diagenetic leaching and alteration, are chemically stable over geologic time, and have occurrences and abundances that are species specific. From hue, chroma and saturation results for the colors of these fossils by comparison to a Munsel color chart, discriminant function analysis indicates that based on coloration alone, these crinoids sort into their morphologically determined classes. Therefore, these molecules are candidates to function as a proxy for phylogenetic reconstruction.

Spectroscopic data were analyzed for aqueous and organic extracts for several species of crinoids. Identifiable basal and radial plates or column segments were tested for biomarker molecules, and spectral data of the organic molecules present in the crinoids were obtained by UV-Vis, Fluorescence, HPLC (High Performance Liquid Chromatography), and GC-MS (Gas Chromatography - Mass Spectrometry). Results obtained by UV-Vis spectroscopy and spectrofluorometry indicate the presence of anthraquinone molecules in Mesozoic crinoids, and other biomarker molecules are present in Paleozoic crinoids. GC-MS enabled identification of many biomarker molecules present in fossil extracts; however, some biogenic molecules are yet to be positively identified. Complex quinone molecules in the extracts were analyzed for their utility as trackable characters for phylogenetic analysis and their distribution compares favorably with the inferred phylogeny of crinoids based on morphology.