Extinction patterns among bivalves in South China during the Permian–Triassic crisis

Abstract

Late Permian Changhsingian bivalves in South China are very abundant and diverse in nearshore, inner shelf, outer shelf, and deep basin facies. All reported data of both bivalve genera and species from the Permian–Triassic boundary strata of South China have been systematically collected and studied for understanding the evolutionary process of various bivalve groups in different environments through the great Permian–Triassic transition. At the genus level, bivalves show an extinction rate of 50% in the first phase of the Permian–Triassic crisis, though only 9.1% in the second phase. There appears to be no selection of extinction in life-style, feeding type or habitat among bivalves from South China through the crisis. There is no significant difference in the extinction rates between epifaunal and infaunal bivalve genera in all environments. Suspension feeders showed moderate extinction rates, while no deposit feeders went extinct at the genus level. In addition, infaunal bivalves were not at more risk of extinction than epifaunal forms. A combination of ocean anoxia and high seawater temperatures might have contributed to the mass extinction among bivalves during the Permian–Triassic crisis.