Flourishing After the End-Permian Mass Extinction

摘要

Two hundred and fifty-two million years ago, the Paleozoic Era came to a cataclysmic close with the end-Permian mass extinction, when as much as 85% of readily fossilizable marine species became extinct. It took 5 million years for the biosphere to begin to recover from the event. At least this has been the conventional view. However, on page 1118 of this issue, Brayard et al. (7) show that ceratitid ammonoids (see the figure, panel A) recovered much faster than did most other marine groups, attaining considerable diversity just 1 million years after the mass extinction. Moreover, these mollusks reached a peak in their diversity at the end of the Early Triassic, when the diversity and body size of most other groups (particularly bivalves and gastropods) was still depressed (2). What do these data tell us about the post-apocalyptic world of the Early Triassic, and about the cause of the end-Permian extinction event itself?