POST-EXTINCTION ECHINODERMS IN THE LATE DEVONIAN WORLD: IMPLICATIONS FOR EVOLUTION AND BIOGEOGRAPHY

Historically, Famennian (Late Devonian) and earliest Carboniferous echinoderms have been poorly known on a global basis, which has resulted in interpretations of prolonged rebound from the Devonian extinction events. Recent discoveries of abundant and diverse Famennian echinoderm faunas from northwestern China, Colorado, Australia, Morocco, and Iran, together with re-examination of previously known Famennian echinoderm faunas from Germany and England, have altered drastically our understanding of the timing and distribution of extinction and rebound of Famennian and earliest Carboniferous echinoderm communities. Overall Famennian echinoderm diversity and abundance is nearly five times greater than previously thought, and new discoveries continue to add to that knowledge. Despite the increases in numbers and diversity, Famennian echinoderm faunas show a dearth of camerate crinoids that typify both older and younger faunas. Famennian cladid diversity domination is a harbinger of trends that appear later in the Carboniferous. One of the Chinese Famennian faunas is dominated numerically by blastoids, which also portends trends seen at various times later in the Paleozoic. From a taxonomic perspective, many Famennian cladids exhibit a combination of characters within single specimens that later separate, stabilize, and define cladid families in the Carboniferous. Blastoids exhibit for the first time the combination of morphologic characters that define dominant genera in the Permo-Carboniferous. From a biogeographic perspective, Laurasian faunas from China and Western Europe have many genera in common. The same cannot be said about Gondwanan faunas, however. In general, we are able to recognize the following trends: 1) echinoderm extinction rebound occurred earlier than previously thought; 2) higher-level taxonomy was not as well established as in older and younger faunas; and 3) biogeographic endemism was less prevalent than in older and younger faunas.