How catastrophic was the end‐Triassic mass extinction?

Abstract

A review of marine and terrestrial animal and plant fossils fails to reveal convincing evidence of a global catastrophe at the Triassic-Jurassic boundary, although this time marked the nal disappearance of ceratite ammonites and conodonts, together with the extinction of most calcareous demosponges; important groups of bivalves and brachiopods went extinct. Because of facies problems, however, there is no stratigraphic section that reveals a clear-cut disappearance over a short distance. Other marine animal groups except perhaps the radiolarians fail to reveal a notable extinction of global extent immediately across the boundary. On the other hand, there was a substantially higher extinction rate among marine animals in the Rhaetian as compared with the previous stage. On the land, the record is equivocal. Dramatic changes across the T-J boundary have been claimed for plants in particular areas, such as eastern North America and East Greenland, but only gradual change has been recognized elsewhere. Similarly, claims of a T-J boundary vertebrate mass extinction have not been supported by others. For the Rhaetian as a whole, however, the turnover rate of reptiles was high. Although much remains to be learned, it seems evident that the fossil record of the latest Triassic is more consistent with a gradual scenario extended over time than a 'geologically instantaneous' impact catastrophe. & Catastrophe, mass extinction, TriassicJurassic boundary A. Hallam (A.Hallam@bham.ac.uk),

Extinction-Recovery Pattern of Level-Bottom Faunas Across the Triassic-Jurassic Boundary in Tibet: Implications for Potential Killing Mechanisms

“…In the extinction pattern, selectivity against infaunal filter-feeding bivalves and taxa with completely aragonitic shells emerges, but no major clade or ecological group finally disappeared. This is a major difference to reef communities, in which several previously important groups became either extinct (e.g., spongiomorphs) or marginalized (e.g., sphinctozoids; Hallam, 2002). The most striking difference to reef communities, however, is the nearly instantaneous rebound, which is in sharp contrast to the 8-10-million-years duration of the reef eclipse.…”

Resetting the evolution of marine reptiles at the Triassic-Jurassic boundary

“…Indeed, it has been argued that the Tr-J event had little effect on marine reptilian evolution, because major clades such as the ichthyosaurs and the plesiosaurs passed through the mass extinction event, rapidly recovered to preextinction diversity levels, and retained many of their ecological roles (4,5).…”

“…The Triassic-Jurassic (Tr-J) transition is marked by a mass extinction that may have been a single event or may incorporate earlier pulses of extinction in the Rhaetian (3)(4)(5), but its role in resetting the dominance of apex marine predators has not been fully recognized (1,3). Indeed, it has been argued that the Tr-J event had little effect on marine reptilian evolution, because major clades such as the ichthyosaurs and the plesiosaurs passed through the mass extinction event, rapidly recovered to preextinction diversity levels, and retained many of their ecological roles (4,5).…”

Treatise Online no. 39: Part N, Revised, Volume 1, Chapter 25: Early Triassic–Early Jurassic bivalve diversity dynamics

“…A special problem was the time value of Rhaetian faunas in papers published prior to the redefinition of this stage by DagYS and DagYS (1994). The Kössen Formation in Austria, the Gabbs Formation in the United States, and the Otapirian deposits in New Zealand at least were considered to be truly Rhaetian in age (DagYS & DagYS, 1994;hallaM, 2002). The time ranges used here are observed ranges defined by first appearances (FADs) and last appearances (LADs) and are therefore only proxies for actual origination and extinction times.…”