Comparative Taphonomy of Marine Benthos: Quantitative Estimates of Higher-Taxon Fidelity in Marine Nearshore Ecosystems of the Outer Banks, North Carolina

While taphonomic biases have been well studied for more heavily biomineralized organisms (such as mollusks), other taxonomic groups have received relatively little attention, and few studies include multiple phyla in their analyses. Consequently, we lack quantitative estimates on relative taphonomic biases across major fossil taxa (i.e., Higher-Taxon Fidelity).

In an effort to quantitatively assess potential taphonomic biases in the fossil record across multiple taxonomic groups with variable biomineralization (bivalves, gastropods, echinoids, decapods and chelicerates), we sampled multiple sites on Outer Banks (North Carolina, USA). Intertidal and subtidal surface and subsurface samples were compared with the living populations from the same sites. All visible biological surface material was collected during low tide from a marked transect on the beach. Once all of the surface material was collected, subsurface samples were taken from the same transect. All material was taphonomically scored to assess taphonomic alteration and preservation potential. In addition, dredge material provided estimates of the subtidal benthos for comparison between the local living populations and the resulting death assemblage. Thus, estimates can be made of which taxa are represented in the death assemblage, and in what quantities. The resulting estimates can be further improved by resampling the same sites. This should allow us to estimate in future short-term changes in both living populations and death assemblages.

Not surprisingly, initial results suggest the presence of strong relative biases: the death assemblage is overwhelmingly dominated by mollusk remains, whereas arthropods and echinoderms are dramatically underrepresented comparing to living communities. These results offer rigorous comparative estimates of the relative quantitative bias in preservation across major higher taxa for one specific study area. The results obtained here represent an empirical data point toward developing a general predictive model for expected fidelity of higher taxa in intertidal-to-subtidal marine depositional systems.