Palaeoecology of the conodonts Hindeodus and Clarkina during the Permian–Triassic transitional period

Detailed investigation of the distributions of the Hindeodus and Clarkina (Neogondolella) conodont faunas has been undertaken on the P/T boundary strata of the Meishan section, Zhejiang Province, South China, in association with detailed facies analysis. This reveals that Hindeodus increased and Clarkina sharply declined in abundance during a phase of relative sea-level rise which began at the end-Permian (Bed 25) and extended into Early Triassic. This was associated with the development of anoxic conditions. This distribution does not accord with previous suggestions that Hindeodus was a nearshore, shallow water taxon. The decline of the supposed deeper water genus Clarkina is also somewhat surprising but it may relate to the inhibition of a nektobenthic genus by dysoxic–anoxic bottom waters. The widespread facies and geographic distribution of Hindeodus suggests it was a pelagic type unaffected by anoxic bottom waters. Hence, the Hindeodus lineage provides a reliable criterion for identification of the Permian–Triassic boundary.