SUBSTRATE AFFINITY IN CARBONIFEROUS ECHINOIDS

Despite the wealth of knowledge concerning echinoid substrate preference in recent and post-Paleozoic environments, relatively little is known of the environmental distribution and paleoecology of echinoids during the Paleozoic. The Paleozoic echinoids encompass the vast majority of the echinoid stem group, and the first crown group echinoids are not known until the Permian. Stem group echinoids are generally rare, but often present in Carboniferous communities across a range of paleoenvironments. We thus analyzed substrate preference in stem group echinoids during the Carboniferous period, utilizing a dataset of echinoid occurrences compiled from museum collections and the literature. We focused on preference for substrate mineralogy (carbonate vs. siliciclastic) and grain size (fine-grained vs. coarse-grained). Using three different quantitative metrics, we analyzed substrate preferences in five families of echinoids, the Palaechinidae, the Archaeocidaridae, the Proterocidaridae, the Lepidesthidae, and the Lepidocentridae. Broadly, we found that most families showed preference for fine-grained, carbonate environments. The palaechinids showed a strong affinity for carbonate environments and were relatively more tolerant of coarse-grained environments than other echinoids. The Archaeocidaridae showed the widest environmental tolerance of any clade, with a high tolerance for siliciclastic and coarse-grained substrates. The Proterocidaridae and Lepidesthidae tended to have a relative affinity for fine-grained substrates. These differential tolerances and affinities for particular environments may have controlled the varying macroevolutionary history of these clades in the Late Paleozoic.