QUANTIFYING THE FIDELITY OF THE FOSSIL RECORD ACROSS MULTIPLE HIGHER TAXA IN NEARSHORE MARINE MACRO-INVERTEBRATE ASSEMBLAGES (NORTH CAROLINA USA)

Understanding the relative fidelity of multiple higher taxa is critical for studying large-scale patterns in the fossil record, where multiple groups are analyzed jointly to assess macro-evolutionary models. Yet few taphonomic studies include more than one phylum, and quantitative analyses comparing living communities with sympatric death assemblages are typically restricted to more heavily calcified organisms such as mollusks. Consequently, our understanding of whole assemblage fidelity and relative taphonomic biases across higher taxa remains limited.

To evaluate fidelity across higher taxa, samples of sympatric live and death assemblages were collected via dredging in coastal North Carolina (USA). Taphonomic biases across invertebrate groups with variable biomineralization (bivalves, gastropods, brachiopods, arthropods, annelids, and echinoids) were assessed. Invertebrate species diversity and relative abundance for live and sympatric death assemblages, were examined at 53 localities representing of a range of depths and nearshore environments. Relative fossilization potential was then estimated for each major taxonomic group.

Dredging resulted in 12,981 live individuals and 58,548 dead individuals, 247 species, and 7 phyla. Locality richness is moderately correlated between live and dead samples (R² = 0.4). Preservation potential is highest for more heavily biomineralized taxa with fewer skeletal components, such as mollusks, and somewhat lower for those with little or no biomineralization and multiple skeletal elements, such as annelids, echinoderms, and arthropods. Whereas a single case study cannot provide universally applicable quantitative generalizations about comparative fidelity of higher taxa, it should nevertheless offer a starting point toward developing numerically-grounded strategies for considering taphonomic overprints in multi-taxic analyses of the fossil record.