Global warming triggered the development of giant dinosaurs. An international team of paleontologists, including LMU professor Oliver Rauhut, finds evidence of the rapid climate change 180 million years ago as the cause of the spread of the known long-necked dinosaurs.
When we hear the word dinosaur, most of us probably immediately think of giant animals with massive bodies, long necks and tails, and tiny heads. These “epitome of dinosaurs” actually represent a prominent subgroup of dinosaurs, the so-called Sauropoda (‘long-necked dinosaurs’ in popular culture). Sauropods were truly amazing animals, and included the largest known land animals, up to 40 m in length and weighing 70 tons or more.
However, these giant animals did not appear right at the beginning of the dinosaur era. During the first fifty million years of their evolutionary history, the sauropodomorpha – the lineage to which the sauropods belong – were represented by several groups of two-legged to four-legged animals. Although some of them already reached large heights of about ten meters in length and several tons in weight, these groups also included smaller and lightly built animals, some of which were no larger than a goat. In addition, all of these animals had rather slender teeth, suggesting that these herbivorous animals ate rather soft and lush vegetation. Towards the end of the early law All of these groups suddenly disappeared around 180 million years ago, and only one line survived and thrived – the sauropods. What caused this faunal change during the early Jurassic has so far remained a mystery.
An international team of researchers led by the Argentine paleontologist Diego Pol and the Munich researcher Oliver Rauhut from the Ludwig Maximilians University and the Bavarian State Collection for Paleontology and Geology are now reporting on new findings about what might have caused these changes. In the province of Chubut in Patagonia, Argentina, they not only discovered the fossil remains of one of the oldest known large sauropods, which the team named Bagualia alba, but could also put it very precisely in its temporal and ecological context. The strata from which the new sauropod originated could be dated very precisely to 179 million years, shortly after the mysterious disappearance of the other sauropodomorphic groups and the discoveries of plant fossils in rock strata shortly before and at that time Bagualia alba lived provide evidence of the climate and ecology in which these animals lived.
So the data show that the climate changed relatively quickly about 180 million years ago, from a temperate warm and humid climate in which diverse, lush vegetation flourished, to a highly seasonal, very hot and dry climate characterized by is a less diverse flora dominated by forms that have adaptations to hot climates, such as B. certain conifers. These environmental changes were apparently due to a greenhouse effect, which was due to greenhouse gases such as CO2 and methane, which were caused by increasing volcanism at the time. Evidence of these volcanic eruptions can be found on many southern continents, for example in the Drakensberg in southern Africa.
With their slender teeth, the non-sauropodan sauropodomorphs were adapted to the rather soft vegetation that was blooming before this event of global warming. However, when this flora was replaced by the much harsher greenhouse vegetation, these animals died out. The only group of sauropodomorphs with much more robust dentition that was well suited to such harsh vegetation, the sauropods flourished and became the dominant group of herbivorous dinosaurs at the time. In fact, specializing in this type of vegetation was probably one of the reasons these animals reached their gigantic size: since large digestive chambers are required to deal with such food, there has been a general tendency for these animals to get bigger and bigger .
Reference: “Herbivorous Dinosaur Extinction Associated with the Global Warming Event of the Early Jurassic” by D. Pol, J. Ramezani, K. Gomez, JL Carballido, A. Paulina Carabajal, OWM Rauhut, IH Escapa and NR Cúneo, 18. November 2020, Royal Society procedure B..
DOI: 10.1098 / rspb.2020.2310