Late Triassic Extinction Event Research Articles

A giant Late Triassic ichthyosaur from the UK and a reinterpretation of the Aust Cliff 'dinosaurian' bones.

The largest reported ichthyosaurs lived during the Late Triassic (~235–200 million years ago), and isolated, fragmentary bones could be easily mistaken for those of dinosaurs because of their size. We report the discovery of an isolated bone from the lower jaw of a giant ichthyosaur from the latest Triassic of Lilstock, Somerset, UK. It documents that giant ichthyosaurs persisted well into the Rhaetian Stage, and close to the time of the Late Triassic extinction event. This specimen has prompted the reinterpretation of several large, roughly cylindrical bones from the latest Triassic (Rhaetian Stage) Westbury Mudstone Formation from Aust Cliff, Gloucestershire, UK. We argue here that the Aust bones, previously identified as those of dinosaurs or large terrestrial archosaurs, are jaw fragments from giant ichthyosaurs. The Lilstock and Aust specimens might represent the largest ichthyosaurs currently known.

Bolide impact triggered the Late Triassic extinction event in equatorial Panthalassa.

Extinctions within major pelagic groups (e.g., radiolarians and conodonts) occurred in a stepwise fashion during the last 15 Myr of the Triassic. Although a marked decline in the diversity of pelagic faunas began at the end of the middle Norian, the cause of the middle Norian extinction is uncertain. Here we show a possible link between the end-middle Norian radiolarian extinction and a bolide impact. Two palaeoenvironmental events occurred during the initial phase of the radiolarian extinction interval: (1) a post-impact shutdown of primary and biogenic silica production within a time span of 104–105 yr, and (2) a sustained reduction in the sinking flux of radiolarian silica for ~0.3 Myr after the impact. The catastrophic collapse of the pelagic ecosystem at this time was probably the dominant factor responsible for the end-middle Norian conodont extinction.

Proliferation of Oberhauserellidae during the recovery following the Late Triassic extinction: paleoecological implications

A paleoecological study of benthic foraminifera through the lower Hettangian in the Doniford Bay section (west Somerset, U.K.) is presented. The sudden and brief appearance of Oberhauserellidae in the aftermath of the Late Triassic extinction is defined as a proxy for environmental perturbations indicating severe biotic stress conditions. Oberhauserellidae, associated with the genus Reinholdella are distinguished from other species by a high abundance, low diversity, high dominance and an abnormally small size. This suite of characters mimics an opportunistic behavior where these r-strategists and grazer feeders maximize their full ecological potential at a time of low-oxygen conditions on the sea-floor and a high food supply: both of which appear to be the main triggers of this paleoecological change. The disappearance of these opportunistic benthic foraminifera coincides with the appearance of infaunal, low-oxygen-tolerant generalists, and the restoration of stable environmental conditions (e.g., well-stratified water mass and oligotrophic conditions), characterizing the initial stages of recovery following the Late Triassic extinction event.

Elevated pCO2 leading to Late Triassic extinction, persistent photic zone euxinia, and rising sea levels

The Late Triassic mass extinction event is the most severe global warming–related crisis to have affected important extant marine groups such as scleractinian corals, and offers potential insights into climate change scenarios. Here we present evidence from Chlorobi-derived biomarkers of episodic and persistent photic zone euxinia. From biomarkers and stable carbon isotopes, we present evidence of rapid mixing of atmospheric and oceanic carbon reservoirs. Global versus regional trends are resolved in kerogen organic matter type, carbonate δ13C, and bulk and pyrite δ34S. This suite of data demonstrates for the first time a comprehensive organic and stable isotope geochemical reconstruction of events leading up to the Late Triassic extinction event and its aftermath. The cascade of events prior to, during, and after the extinction is remarkably similar to those reported for the Late Permian extinction, the largest extinction event of the Phanerozoic. We predict that similar conditions will have occurred during all past episodes of rapid global warming and biotic crisis that are associated with similar rises in p CO2.

Palaeoecology of the Late Triassic extinction event in the SW UK

A high-resolution palaeoecological study of the shelly invertebrate macrofauna across two marine Triassic–Jurassic boundary sections in the UK (St. Audrie's Bay and Lavernock Point) is presented. Loss of taxonomic richness occurs in the upper Westbury Formation to lower Lilstock Formation (late Rhaetian), but if sample size is taken into account there is little convincing evidence of a catastrophic marine extinction. There is, however, good evidence for significant palaeoecological change in the benthic marine ecosystem at this time. The immediate post-event recovery interval in the upper Lilstock Formation is characterized by assemblages of low abundance, low diversity, high dominance and low evenness. Body-sizes of taxa that survived the event and originated afterwards were low until the later Hettangian. Recovery to higher abundance, higher diversity and higher evenness is recorded in the Psiloceras planorbis Zone. Recovery of the benthic ecosystem in the aftermath of the Late Triassic event was disrupted by marine anoxia and shows additional similarities to the (much slower) recovery that followed the Late Permian event. The pattern of body-size changes recorded in the shelly fossil record closely matches that of the trace fossil record. Shell thickness trends do not support a biocalcification crisis during the Late Triassic biotic event.