Size reduction of conodonts indicates high ecological stress during the late Frasnian under greenhouse climate conditions in South China

Abstract

The Late Frasnian mass extinction (LFME) during extreme greenhouse conditions had a serious impact on biotic evolution. Herein, based on detailed size measurements of 1783 elements of the conodont genera Polygnathus and Palmatolepis at the Lali and Duan sections in South China, conodont animals underwent significant size reduction at the genus level during the late Frasnian. The “Bergmann's rule” controlled the evolution of Frasnian conodont animals, and their size reduction during the late Frasnian may have resulted from long-term global warming and indicated high ecological stress before the Frasnian-Famennian boundary (FFB). This phenomenon can explain why the decline of benthic faunas, such as corals, brachiopods or metazoan reefs, predated the extinction of pelagic faunas, such as conodonts in the Upper Kellwasser (UKW) event and at the FFB.