The Famennian (Late Devonian) Diversification of Echinoderms

The Mississippian Period is often called the Age of Echinoderms because of the high generic diversity and abundance of crinoids and blastoids worldwide. Historically Famennian (Late Devonian) and earliest Carboniferous echinoderms have been poorly known on a global basis leading to interpretations of prolonged rebound from Devonian extinction events and subdued origination in the Late Devonian. Recent discoveries of Famennian echinoderm faunas from China, Colorado, Australia, and Iran, together with continued studies of faunas from Germany and England, have changed our understanding of the patterns of extinction and rebound of Famennian and earliest Carboniferous echinoderm communities. Overall, Famennian diversity at the generic level for crinoids and blastoids 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. Rebound from the Late Devonian extinction events in echinoderms and origination at the generic and familial level were more rapid than previously thought, but seem to be concentrated in Asian faunas. These faunas are found in a variety of environmental settings, but the most abundant and diverse Famennian fauna from Asia occurs in the Hongguleleng Formation, which was deposited in a tectonically active island arc setting rather than a carbonate platform or ramp setting in which we more commonly find large echinoderm communities. This suggests that the key to finding rebound faunas after some mass extinction events may be to look in geographic areas and tectonic settings that are very different than those occupied by the precursor or successor faunas.