9316279 Cobabe Bivalve shells are common fossils in near-shore marine strata from the early Paleozoic to the Recent. The diversity and abundance of bivalves makes them an important research target for molecular paleontology. Based on our preliminary research, the geologically stable and easily extracted class of compounds known as lipids offers a promising new approach to interpreting the biogeochemical record of bivalves. Recent and fossil shells contain a wide variety of mineral-associated lipids, including fatty acids, cholesterol, ketones, phytadienes, and alkanes. The shell-lipid assemblages contain compounds that are 1) present in all of the studied bivalves (recent and fossil), 2) specific to a single taxon, and 3) environmentally specific. In the cases of extraordinary fossil preservation, lipids trapped in the shell may provide a clean molecular and isotopic record of trophic strategy, biosynthetic pathway, and paleoenvironmental conditions. We propose utilizing the molecular structure and 13C content of shell lipids to determine the biogenic source of the compounds. We will then apply these compounds to studies of 1) chemosymbiosis in the fossil record and 2) the use of fatty acid saturation to assess paleotemperature.
