Brachiopod survival and recovery from the latest Ordovician mass extinctions in South China

Abstract

South China contains many complete sections through the upper Ordovician and lower Silurian. Brachiopod data including 130 brachiopod genera, assigned to 13 orders and 27 superfamilies from mid-Ashgill through late Aeronian intervals reveal that brachiopod macroevolution before and after the latest Ordovician mass extinction shows important changes in the diversity, composition and stratigraphical distribution of the phylum. The following six intervals are recognized: (1) a faunal plateau before the latest Ordovician mass extinction (mid-Ashgill, Rawtheyan); (2) a survival–recovery interval following the first phase of the mass extinction (late Ashgill, Normalograptus extraordinarius Zone and lower Glyptograptus? persculptus Zone; Hirnantian); (3) first survival interval following the mass extinction (latest Ashgill, upper Glyptograptus? persculptus Zone; end Hirnantian); (4) a second survival interval after the mass extinction (earliest Llandovery, Parakidograptus acuminatus Zone; early to mid-Rhuddanian); (5) a recovery interval in the Silurian (early to mid-Llandovery; late Rhuddanian to early Aeronian); and (6) a radiation interval in the Silurian (mid-Llandovery; mid- to late Aeronian). Only near-shore, low-diversity, benthic assemblages (mainly BA2), characterized by Ordovician relicts with a few Lazarus taxa and progenitors, are known from the southern marginal area of the Upper Yangtze epicontinental sea during the early to mid-Rhuddanian. They were replaced by newly established Silurian brachiopod communities (mainly BA2–3) in the late Rhuddanian to early Aeronian. These are marked by many newly evolved endemic forms and new immigrants, expressing a clear recovery within the Brachiopoda, but the recovery interval of the major brachiopod groups was heterochronous. In China the typical Silurian brachiopod fauna was mainly composed of indigenous Atrypida, Pentamerida and Spiriferida with stropheodontids derived from elsewhere, such as Baltica and Avalonia, two apparent refugia in the survival interval. The Atrypida was the first major group of Brachiopoda to diversity in the late Rhuddanian. Copyright © 1999 John Wiley & Sons, Ltd.