INTRINSIC AND EXTRINSIC ECOLOGICAL DETERMINANTS OF EXTINCTION AT THE END-TRIASSIC MASS EXTINCTION

The end-Triassic extinction (c. 201 Ma) is recognised as one of the “Big Five” mass extinction events, resulting in an estimated loss of 34% of marine genera and ranked third, in terms of ecological severity, amongst Phanerozoic extinctions. Here, we assess the ecological effect of the mass extinction on marine communities along with the functional patterns of recovery into the Early Jurassic. Using the Bambach ecospace model – based on unique combinations of three variables focusing on mobility, feeding, and tiering – we show that, although taxonomic extinction was severe, extinction amongst functional groups was less so, with only a few modes of life apparently disappearing at the end of the Triassic. We also assess how intrinsic and extrinsic ecological factors influence extinction intensity. Generic extinction was highest in the northern polar latitudes and the tropics, and Panthalassan taxa suffered higher extinction rates than taxa residing in the Tethys and Boreal oceans. Reef dwelling taxa suffered the highest levels of extinction, whilst those inhabiting inner-shelf environments were the least affected. An erect benthic or pelagic mode of life appears to have been most susceptible to extinction whilst suspension feeders and grazers suffered higher extinction rates than taxa displaying other feeding strategies. Non-motile and highly mobile taxa appear to have suffered higher levels of extinction than slow moving and facultatively mobile taxa. The results show that both intrinsic and extrinsic ecological factors have a bearing on whether taxa are more or less likely to survive a mass extinction event.