A re-evaluation of Famennian echinoderm diversity: implications for patterns of extinction and rebound in the Late Devonian

Abstract

AbstractCritical to understanding long-term trends in diversity is a dataset that is both worldwide in scope and based on a sound taxonomic foundation. In this paper we re-evaluate the Famennian (Late Devonian) echinoderm dataset, which has changed radically in the past decade, and reinterpret patterns of Late Devonian echinoderm extinction and rebound based on these new data. Historically, Famennian (Late Devonian) and earliest Carboniferous echinoderms have been poorly known on a global basis leading to interpretations of prolonged rebound from the Devonian extinction events. Recent discoveries of abundant and diverse Famennian echinoderm faunas from northwestern China, Colorado, Australia and Iran, together with re-examination of previously known echinoderm faunas from Germany and England, have altered drastically our understanding of the patterns of extinction and rebound of Famennian and earliest Carboniferous echinoderm communities. Overall, Famennian echinoderm diversity at the generic level is nearly five times greater than reported in the 2002 Sepkoski compilation, and familial level diversity is more than seven times greater than previously thought. Despite the increases in diversity, Famennian echinoderm faunas show a reduced diversity of camerate crinoids that typify both Middle Devonian and Lower Mississippian faunas and portend the rise of cladid crinoid diversity later in the Carboniferous. Individual Famennian faunas are numerically dominated by blastoids, which also portends trends seen at various times later in the Palaeozoic. In general, we are able to recognize the following trends. Rebound from the Late Devonian extinction events in echinoderms was more rapid than previously thought, but seems to be concentrated in Asia. Palaeogeographically Famennian echinoderms can be grouped into two broad regions: one includes China, Australia and Iran, all of which bordered the Palaeotethys; the other includes regions from Laurussia (Europe and North America) and northern Africa (Morocco).