Extinction of herbivorous dinosaurs linked to Early Jurassic global warming event

Abstract

Sauropods, the giant long-necked dinosaurs, became the dominant group of large herbivores in terrestrial ecosystems after multiple related lineages became extinct towards the end of the Early Jurassic (190–174 Ma). The causes and precise timing of this key faunal change, as well as the origin of eusauropods (true sauropods), have remained ambiguous mainly due to the scarce dinosaurian fossil record of this time. The terrestrial sedimentary successions of the Cañadón Asfalto Basin in central Patagonia (Argentina) document this critical interval of dinosaur evolution. Here, we report a new dinosaur with a nearly complete skull that is the oldest eusauropod known to date and provide high-precision U–Pb geochronology that constrains in time the rise of eusauropods in Patagonia. We show that eusauropod dominance was established after a massive magmatic event impacting southern Gondwana (180–184 Ma) and coincided with severe perturbations to the climate and a drastic decrease in the floral diversity characterized by the rise of conifers with small scaly leaves. Floral and faunal records from other regions suggest these were global changes that impacted the terrestrial ecosystems during the Toarcian warming event and formed part of a second-order mass extinction event.

Earliest evidence of herd-living and age segregation amongst dinosaurs

“…200 Ma), which left them as the only large herbivores in terrestrial ecosystems of the Early Jurassic 4,6 . The predominance of early sauropodomorph dinosaurs in terrestrial ecosystems extended for almost 40 million years 7 (ca. 220-180 Ma, Norian-Pliensbachian 8 ).…”

“…6 CONICET, Instituto de Investigación en Paleobiología Y Geología, Universidad Nacional de Río Negro, Museo Carlos Ameghino, Belgrano 1700, Paraje Pichi Ruca (Predio Marabunta), Cipolletti, Río Negro, Argentina. 7 CONICET, División Paleontología de Vertebrados, Museo de La Plata, Paseo del Bosque s/n (1900) La Plata, Buenos Aires, Argentina. 8 European Synchrotron Radiation Facility, 71 avenue des Martyrs, 38000 Grenoble, France.…”

Sauropodomorph evolution across the Triassic–Jurassic boundary: body size, locomotion, and their influence on morphological disparity

“…The new region of the morphospace occupied during the Toarcian-Middle Jurassic (Fig. 2c) represents the emergence of new lineages distinguished by a unique body plan (e.g., Vulcanodontidae, Gravisauria, Eusauropoda) of obligatory quadrupedal stance, elongated forelimbs, and columnar limbs, all features interpreted as related to their large body mass 20,22,38 (Figs. 1a,e, 2d).…”

“…1, 2c), and reflects the significant body plan changes of Sauropodomorpha at this time. At the same time, the significantly lower Toarcian-Middle Jurassic disparity values of the pelvic girdle and hindlimb is probably related to the extinction of non-sauropodan sauropodomorphs by the late Pliensbachian 20,38 that left gravisaurian sauropods as the only surviving sauropodomorphs. This same pattern has been recovered for the pelvic girdle using geometric morphometrics, but not for the cranium 45 .…”

“…Finally, a major event in sauropodomorph evolution is the diversification of gravisaurian sauropods, implying numerous changes in their body plan, locomotion, feeding behaviour, and extremely large body size 20,[22][23][24]39,40,55 . This event represents a second expansion of morphospace towards previously unexplored regions (Figs.…”