Extinction: End‐Triassic Mass Extinction

Abstract

One of the five greatest mass extinction events in Earth's history occurred at the end of the Triassic, c . 200 million years ago. This event ultimately eliminated conodonts and nearly annihilated corals, sphinctozoan sponges and ammonoids. Other strongly affected marine taxa include brachiopods, bivalves, gastropods and foraminifers. On land, there is evidence for a temporal disturbance of plant communities but only few plant taxa finally disappeared. Terrestrial vertebrates also suffered but timing and extent of this extinction remain equivocal. The cause of the end‐Triassic mass extinction was probably linked to the contemporary activity of the Central Atlantic Magmatic Province, which heralded the breakup of the supercontinent Pangaea. Possible kill mechanisms associated with magmatic activity include sea‐level changes, marina anoxia, climatic changes, release of toxic elements and compounds and ocean acidification. Recovery from the extinction event was remarkably fast for marine level‐bottom faunas but delayed for reef communities, possibly because reef organisms were more co‐evolved and suffered higher losses during the extinction. Key Concepts Nearly half of all marine genera and a smaller but still significant proportion of terrestrial taxa went extinct at the end of the Triassic period, c . 200 million years ago. The end‐Triassic mass extinction took place during a geologically short time interval, which coincided with the onset of massive magmatic extrusions along fracture zones of the disassembling supercontinent Pangaea. A cause‐and‐effect relationship between magmatic activity and mass extinction is indicated by the accordance of predicted extinction patterns and observed data from the fossil record. Ocean acidification as a kill mechanism in marine ecosystems is confirmed by preferential extinction of taxa with thick aragonitic skeletons. The end‐Triassic mass extinction event provides a test case for studying evolutionary responses to major environmental disturbances on the global scale and over geological time. Although there are differences in emission rates, the massive magmatic CO 2 release at the end of the Triassic is quantitatively similar to a potential release by complete combustion of the global fossil fuel reserves. A prediction from data of the fossil record for marine ecosystems is that level‐bottom communities are able to recover much more quickly from the effects of excess CO 2 than reefs.

Gastropods underwent a major taxonomic turnover during the end-Triassic marine mass extinction event

“…We therefore refer to the "T-J faunal transition" rather than "T-J mass extinction" in the discussion of our data. However, there is much evidence for a sudden extinction in the latest Triassic from numerous case studies ( [2] and refs therein), and we interpret our data in that light.…”

“…There is an increasing consensus that the end-Triassic mass extinction was caused by a number of environmental changes that resulted from the contemporaneous volcanism of the Central Atlantic Magmatic Province (CAMP); these include climatic changes, ocean acidification, sea level changes, marine anoxia, and the emission of toxic elements and compounds (see summary in [ 2 ]). Our data allow for testing the first two of these possible causes.…”

“…The end-Triassic mass extinction is commonly ranked among the “big five” extinction events of the Phanerozoic [ 1 ] and has attacked considerable scientific attention [ 2 ], but surprisingly, there is still a lack of comprehensive studies on the taxonomic turnover for many major taxa. Probably the most prominent example for this lack of knowledge is the gastropods.…”