[Animals] The strange armored dinosaurs that po[CENSORED]ted South America

[Draeno]

 

About 100 million years ago, Patagonia was home to one of the largest carnivores that has ever existed on Earth: the Giganotosaurus carolinii, between 12 and 13 meters long and almost seven tons, somewhat larger even than the mythical Tyrannosaurus. rex, with which he rivals in the latest film in the Jurassic World saga. It was an amateur fossil hunter, Rubén Carolini, who in 1993 discovered the first fossil of this lethal predator; And in the 30 years since then, Argentine Patagonia has become a mecca for paleontological research and scientific tourism.

Considered a world factory for dinosaurs, the region has the most important paleontological collection in South America, where more than 30 new types of dinosaurs from the late Cretaceous period, between 90 and 100 million years ago, have been discovered. In the middle of its desert landscape, museums dedicated to these prehistoric reptiles flourish. And fabulous discoveries continue to be made at its deposits, changing the ideas we had about the evolution of dinosaurs on this continent.

The latest of these surprising finds is the new species named Jakapil kaniukura, which means stone-crested shield bearer, in the ancestral languages of northern Argentine Patagonia. This armored dinosaur was no bigger than a domestic dog. He was less than five feet tall and weighed between four and seven kilos. It was herbivorous and had much shorter front legs than the hind legs, which indicates that it could run semi-upright; or better, flee at good speed from the fearsome giganotosaurs, with which it coexisted in Patagonia at the same time of the Cretaceous.

The discovery of this species inaugurates a new genus within the thyreophores, a group of dinosaurs characterized by the armor that covers the dorsal and upper part of its body. The best known of this genus are the stegosaurus, with pentagonal plates on a spine topped with thick spines, and the ankylosaurus, covered in a spiny carapace and a club at the tip of its tail.

What was known so far about this large group, which arose in the Jurassic (between 200 and 145 million years ago) on the supercontinent of Laurasia, was that the vast majority of species lived on that huge landmass (above all, in present-day North America, Europe and China) and that evolution led them to be quadrupeds: only the most primitive walked on two legs, like the scutellosaurus. The discovery of the jakapil, however, changes that story in three fundamental ways. Bipedal thyreophores continued to exist for a very long time afterwards (until the late Cretaceous) and spread to other parts of the planet (in Gondwana, the continents below the equator today), where their presence was previously unknown. This also allows us to reason that this lineage probably underwent an evolutionary reduction of its front legs, as happened to other species, such as the tyrannosaurus and the giganotosaurus.

This new species lived in the hostility of the ancient Kokorkom desert (located in the current paleontological area of La Buitrera, in the Argentine province of Río Negro), where everything alive was thorny and hard, including the small jakapil. To survive in this environment, it developed a high and robust jaw that allowed it to eat whatever it found: seeds, succulent plants and even wood. Adorned with a stone crest, his peculiar jaw could also have served as a weapon of seduction, although this is, for now, only conjecture.

The description of this holotype was published in the scientific journal Scientific Reports in 2022, by Argentine researchers Facundo Riguetti and Sebastián Apesteguía, from the Félix de Azara Natural History Foundation, the Maimónides University and the National Council for Scientific and Technical Research ( CONICET). The Spaniard Xabier Pereda, from the University of the Basque Country, also collaborated.

 

https://elpais.com/ciencia/2023-05-27/los-extranos-dinosaurios-acorazados-que-poblaron-sudamerica.html