Carnian Extinction

Extinction within the Carnian is pronounced in many groups, including both marine and terrestrial organisms. In the marine realm, ammonites, crinoids, echinoids, bryozoans, scallops, conodonts, calcisponges, fish, and marine tetrapods exhibit large diversity declines. Meanwhile on land, peaks in the extinction rates of pollen and spores suggest that many species of plants became extinct. In addition, up to 42 percent of tetrapod families, including 66 percent of tetrapod species, became extinct during this interval. The extinctions that occurred during the Carn-ian are also important because they signify a change in the terrestrial realm from the dominance of groups such as rhynchosaurs and mammal-like reptiles prior to the extinction to more modern groups, such as turtles, dinosaurs, and mammals following the extinction. It has been suggested that this extinction may be related to climate change, such as increased rainfall.

Although this event appears to have been dramatic, it has been argued that the Carnian extinction is local and not global in extent, or that it may be an artifact of a poor fossil record, since sea level was low at that time and few marine rocks are preserved. Indeed some groups, such as the majority of bivalves, do not suffer elevated extinction during this interval. Therefore, although some extinction certainly does occur during the Carnian stage, it is uncertain how widespread or dramatic the effects of this event were globally, and whether it should be considered as important an event as the extinction that occurred at the end of the Triassic Period.

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