Deciphering the evolution of sea urchins through the Devonian and Carboniferous: recent advances and open questions

Sea urchins (phylum Echinodermata, class Echinoidea) have an excellent fossil record throughout the Mesozoic and Cenozoic, but their evolutionary history in the Paleozoic is much less understood. A first diversity maximum of Paleozoic (stem-group) echinoids in the Mississippian has long been recognized, and Mississippian forms are taxonomically and morphologically distinct from their Devonian predecessors. Recent work has shown that Famennian echinoids are more similar to Carboniferous forms than to those of the pre-Famennian Devonian, implying faunal turnover around the Frasnian-Famennian boundary. Ongoing research by the author on Devonian and Mississippian echinoids from Germany and Belgium confirms that the family Lepidocentridae, after attaining its maximum diversity in the Frasnian, likely disappeared at the end of the Frasnian, while the Famennian saw the first appearance of the important Late Paleozoic families Lepidesthidae, Proterocidaridae and Archaeocidaridae. New material also confirms an Early Devonian origin of the family Palaechinidae which, after a long ghost lineage spanning most of the Devonian, would become the primary driver of echinoid diversity increase in the Mississippian. Recent research based on large datasets of museum specimens has underscored the impacts of taphonomic and sampling biases as well as the legacy of scientific colonialism on perceived patterns of paleobiodiversity and paleobiogeography in Paleozoic echinoids. To overcome these challenges and identify genuine diversity patterns, detailed and targeted systematic work based on articulated and disarticulated material must be combined with improved understanding of Paleozoic echinoid phylogeny, paleobiology and habitat preferences.