WRITING THE FOSSIL RECORD OF EARLY ANIMAL LIFE: PRESERVATION ACROSS THE EDIACARAN–CAMBRIAN TRANSITION

One of the first lessons in any introductory paleontology class regards the inherent bias of the fossil record. The bulk of our record is comprised of bones, shells, and various other hard parts, but certainly not all living things make such structures. The organisms that produced these hard parts already accomplished most of the work needed for fossilization to occur during life—mineralization, in these cases biologically directed. Yet, we have incredible views of those organisms that did not produce hard parts in vivo—again owing to mineralization, but in these cases externally mediated. Across the Ediacaran–Cambrian transition, organism-directed biomineralization was is in its evolutionary infancy, and thus our window onto the dawn of animal life would have been largely obscured if not for externally mediated mineralization pathways. Nonetheless, discrepant readings of the taphonomic histories of these organisms (that is, how one distinguishes biology from geology, e.g., Cunningham et al. 2012) has often led to debates regarding phylogeny of the organism preserved as well as the preservational pathway itself. This presentation will focus on several case studies of taphonomic mineralization pathways, namely carbonaceous compression, pyritization, and aluminosilicification, observed across the Ediacaran-Cambrian transition. The goals are not only to provide geochemical/geomicrobiological models to explicate the progression and the potential interrelatedness of these taphonomic mineralization modes, but also to help inform their resultant biological fidelity.