Excrement, vomit and fossilized remains of food in the intestine are clues to the spectacular rise of dinosaurs to supremacy over the animal kingdom more than 200 million years ago, according to a study published Wednesday, November 27, in the journal Nature.
Much is known about its existence and disappearance 66 million years ago. But “we know very little about its rise”, a true conquest of the world in about thirty million years, paleontologist Martin Qvarnström of the Swedish University of Uppsala, first author of the study, reminds AFP.
The team of researchers led by paleontologist Grzegorz Niedzwiedzki, also in Uppsala, is carrying out an exhaustive review of more than 500 bromalites, the fossilized remains of what dinosaurs in the Polish Basin digested, vomited and excreted.
By identifying its content and linking it to its producers, researchers “can start to connect who ate who or what,” says Martin Qvarnström. And thus show “how the ecological role of dinosaurs changed over time.”
Ground beetles and bones in feces.
The coprolites, fossilized excrement, were probed with cutting-edge techniques such as synchrotron microtomography. Which reveals almost intact beetles, fish vertebrae or teeth, plant fragments, crushed bones.
Crossing these data with those of paleontology and the evolution of climate and flora, they developed a model of the progressive domination of the dinosaurs. This is illustrated by the average diameter and length of vertebrate bromalites, which tripled in the case of those from the Polish Basin in 30 million years. The size of its owners will continue, throughout this period from the end of the Triassic era to the beginning of the Jurassic.
The “precursors” of the lineage, the Silesaurus, are “quite small”, barely measuring a meter high at the neck and weighing, at best, 15 kilos. But while the dominant animal of the moment, the Dicynodontes, a barrel-shaped quadruped weighing a few tons, feeds exclusively on conifers, the Silesaurus has a great advantage: it is omnivorous.
“By studying its droppings, we see that it eats all kinds of things, a lot of insects, fish and plants,” says Martin Qvarnström.
Opportunistic and omnivorous, it will adapt quickly to radical changes in the environment, such as the Carnian rain episode. Carrier of humidity, it promotes great diversification of the flora. Which surprises the large herbivores of the moment, unable to adapt to this change in diet.
“The dinosaurs were a little lucky”
Silesaurus, and later the long-necked herbivorous dinosaurs, ancestors of Diplodocus, “will feast on these new plants.” As they grew larger and larger, they stimulated the growth of theropods, bipedal and mostly carnivorous dinosaurs.
Thus, at the beginning of the Jurassic, the landscape was dominated by imposing herbivores and ferocious carnivores.
“The dinosaurs were a bit lucky, but they also adapted very well to this changing environment,” summarizes Martin Qvarnström, whose study is careful not to settle the debate about the reasons for this supremacy.
It contrasts the supporters of “competitive exclusion” – which attributes anatomical and physiological advantages to dinosaurs – with the supporters of “opportunistic replacement”, for whom they would have benefited from the disappearance of other groups, recalls paleontology professor Lawrence H. .Tanner, in Le Moyne. Collège, in an article accompanying the study.
A “starting point for future work”
The Uppsala team speculates that a combination of these two approaches crowned the reign of the dinosaurs, with environmental changes coinciding with dietary adaptation.
According to Lawrence Tanner, this research should be seen as a “starting point for future work.” Because although it is based on a “particularly creative methodology”, with a range of notable technical means, it remains “limited in its context and in its extent” to the Polish basin, which was then part of the supercontinent of Pangea.
Martin Qvarnström does not hide it. And he hopes that “the model built in one area may be valid for others,” particularly in southern Pangea, where the first real dinosaurs appeared.
Source: BFM TV
