TERRESTRIAL END OF TRIASSIC EXTINCTIONS: NEITHER SUDDEN NOR SEVERE

Research literature examining the events at the Triassic-Jurassic boundary (TJB) continues to promulgate the misconception of a single mass extinction, including terrestrial plants and animals, at the end of the Triassic. This misconception is based on multiple errors: (A) local studies that demonstrate a biotic turnover at or near the TJB unjustifiably extrapolated to represent a widespread or global event; (B) the compiled correlation effect, which confounds literature-based compilations of biodiversity, such as the Paleobiology Database; and (C) simple miscorrelation of the TJB between nonmarine and marine strata. Error A is best exemplified by the Newark basin “fern spike,” which has never been demonstrated to mark a widespread phenomenon, and regardless, does not occur at the boundary. Similarly, analyses of the paleobotanical record in eastern Greenland suggest a biotic turnover in plants across the TJB, but this turnover is not apparent in the global record despite claims to the contrary. Error B is best seen in literature-based compilations of tetrapod diversity across the TJB, which smear together a prolonged drop in crurotarsan abundance and diversity to look like a single TJB extinction. It is further amplified by mistakes in the dating of key vertebrate ichnotaxa. Error C is best illustrated by decades-long miscorrelation of the TJB in the nonmarine Newark Supergroup. This correlation was based on the circular line of reasoning that because there “must” be a mass extinction at the TJB, the largest biotic turnover in the Newark, a palynological event, must mark the TJB. In fact, this turnover is a within Triassic event. The global record of terrestrial plants documents no significant plant extinctions across the TJB. Among terrestrial tetrapods, most extinctions take place at or just before the Norian-Rhaetian boundary. The terrestrial record of biodiversity across the TJB is one of complex and prolonged turnover characterized by low origination rates and multiple extinction events, similar to the record of the marine realm, where a prolonged interval (several million years) of low origination rates precedes the TJB.