New insights on the correlation of Permo-Triassic terrestrial faunas of South Africa with those of European Russia.

Abstract

The mid-Permian to the mid-Triassic is a fascinating period in tetrapod evolution, witnessing the transition from primitive to modern ecological structures and the rise of archosaurs following the apogee of Palaeozoic therapsid faunas. It also encompasses two major extinction events, of differing magnitude, that are evident in both terrestrial and marine environments. This time period is best known from the fossiliferous sequences of the South African Main Karoo Basin and the sedimentary basins of European Russia. Palaeontological studies over the past 15 years have resulted in numerous discoveries that have refined the biostratigraphic framework of both regions, and independent dating methods have been employed that have further clarified the relationship of the two faunal successions. We present a new regional correlation between the faunal assemblages of these high latitude regions, incorporating this new data. Both are defined by mid-Permian faunas dominated by dinocephalian therapsids, after which tetrapods of Gondwanan origin enter Eurasia in the aftermath of the Capitanian mass extinction event, particularly dicynodonts and theriodont therapsids. Following the end-Permian mass extinction temnospondyls diversified in both regions and archosaurs became more common but, by the mid-Triassic, cynodonts were evolving complex postcanine occlusion in Gondwana but had become extirpated from European Russia.