LIVE-DEAD FIDELITY OF MULTI-TAXIC ASSEMBLAGES: RELATIVE TAPHONOMIC BIASES ACROSS MAJOR BENTHIC MARINE INVERTEBRATE GROUPS (NORTH CAROLINA, USA)

Few taphonomic studies include more than one phylum, despite the fact that multiple phyla are often included in paleontological studies. Quantitative analyses comparing living communities with sympatric death assemblages are typically restricted to a single taxon, primarily 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 the fidelity of multi-taxic assemblages, we collected samples of sympatric live and death assemblages via dredging in coastal North Carolina (USA), to quantitatively assess taphonomic biases across invertebrate groups with variable biomineralization (bivalves, gastropods, brachiopods, decapods, chelicerates, and echinoids). Invertebrate species diversity and relative abundance were estimated for both live and death assemblages, at localities comprising of a range of depths and environments. Localities also include sites variably affected by anthropogenic activities. Relative fossilization potential was estimated for each major taxonomic group and live-dead fidelity was assessed using the Jaccard-Chao Spearman-Rho fidelity plots of Kidwell (2007).

Data thus far are preliminarily, and are based on 75 dredge samples of live benthic marine invertebrates from 28 localities. Samples have yielded over 2,800 live individuals and 5,950 dead specimens representing 135 species from 116 genera, and 9 phyla. Preliminary analyses indicate the presence of strong relative biases: preservation potential is highest for more heavily biomineralized taxa with fewer skeletal components, such as mollusks, and lower for those with little or no biomineralization and multiple skeletal elements, such as echinoderms and arthropods. When all higher taxa are included, dredge samples show low live-dead fidelity (low Jaccard-Chao Spearman Rho coefficients). This pattern persists when the analysis is repeated for mollusks only. This internal consistency agrees with previous studies suggesting that mollusks alone may provide a representative assessment of anthropogenic impacts on benthic marine communities.