Jeffrey Robert Thompson, Christopher D. Dean, Madeline Ford, Timothy A. M. Ewin

Animals with multi-element skeletons, including the vertebrates, echinoderms, and arthropods, are some of the most biodiverse and ecologically important animal groups. Understanding the relative impact of the myriad geological and biological factors which impact on the quality of multi-element skeletal fossils is thus crucial for disentangling perceived changes in biodiversity through time and shedding light on gaps in the fossil record. We have characterised the specimen-level taphonomic history of virtually the entire Palaeozoic fossil record of echinoids, the class of echinoderms which includes the living sea urchins. We find that the majority of this fossil record consists of disarticulated skeletal elements and as preservational quality increases, so does the proportion of specimens which can be identified with higher taxonomic precision. We then assessed the relative impacts of multiple geological and biological factors on our specimen quality, identifying that fine-grained host matrix, as well as siliciclastic lithology are the biggest factors in determining quality of fossil echinoid preservation, while aspects intrinsic to specific taxonomic groups also play a role. Differential sampling of the fossil record seems to play little role in influencing the distribution of taphonomic grades, and fluctuations in the North American record of Siliciclastic rocks are positively correlated with fluctuations in taphonomic grades. Our results highlight that the factors controlling the animal macrofossil record are varied, and that the interplay between these variables, taphonomic grade, and taxonomic precision impacts on our ability to use the fossil record to understand macroevolution.