Dinosaur extinctions related to the Jenkyns Event (early Toarcian, Jurassic)

Abstract

The early Toarcian Jenkyns Event (~183 Ma) was characterized by a perturbation of the global carbon cycle, global warming, which at continental areas led to intensifi ed chemical weathering, enhanced soils erosion, and intensifi ed wildfi res. Warming and acid rain aff ected diversity and composition of land plant assemblages, caused a loss of forests and thereby impacted on trophic webs. The Jenkyns Event, triggered by volcanic activity of the Karoo-Ferrar Large Igneous Province, changed terrestrial ecosystems, and also aff ected the dinosaurs. Fossil macroplant assemblages and palynological data reveal reductions in the diversity and richness of plant communities. A substantial loss of land plant biomass and a shift to forests dominated by Cheiropelidiaceae conifers occurred as a consequence of seasonally dry and warm conditions. Major changes occurred to hervivore dinosaurs, with extinction of diverse basal families of Sauropodomorpha ('prosauropods') as well as some basal sauropods. Ornithischian dinosaurs show patchy records; some heterodontosaurids disappeared and the scelidosaurids (Thyreophora) went extinct during the Jenkyns Event. The dominant carnivorous dinosaurs, the Coelophysoidea (Theropoda), died out during the Jenkyns Event. We interpret the Jenkyns Event as a terrestrial crisis for ecosystems, marked especially by fl oral changes and the extinction of some dinosaur clades, both hervivores and carnivores.