QUALITATIVE AND QUANTITATIVE ASSESSMENT OF TAPHONOMIC PATTERNS IN MODERN ALGAE AND CYANOBACTERIA: IMPLICATIONS FOR IDENTIFYING PRECAMBRIAN MICROFOSSILS

Precambrian microfossils are notoriously difficult to assign to major taxonomic groups. At present, no single set of characters can be used to identify the earliest eukaryotes or to securely place silicified microfossils or compressed acritarchs into domain-level clades. Cell size, cell wall ultrastructure, ornamentation, and biogeochemical characteristics are used separately or in combination to evaluate the systematics of these microfossils. In addition to morphological characteristics, it is plausible that taphonomic characters might also lend insight into the nature of these fossils. In particular, rate and mode of early post-mortem decomposition might be expected to have a taxonomic as well as environmental component, thereby influencing how organisms are represented in the fossil record.

Understanding characteristic taphonomic pattern in diverse groups can aid in recognizing eukaryotes in the Precambrian fossil record. Previous work has evaluated decomposition of algae and cyanobacteria separately; this project aims to make a direct comparison between photosynthetic prokaryotes and eukaryotes and to establish a framework by which other groups (e.g., fungi, animals) can be evaluated. In this research, we report decomposition patterns through qualitative description of trends (e.g., differential decomposition) and through quantitative analysis of decomposition. We describe observed taphonomic trajectories and compare cyanobacterial and algal patterns. Preliminary results indicated that there are characteristic differences between major groups. Based on these initial findings, taphonomic characters may be useful, when combined with traditional taxonomic characters, in inferring phylogenetic placement of Precambrian microfossils.