The giant dinosaur with a ridge of thorns discovered in Argentina | Nature

But its most extraordinary feature is the ridge full of huge spines that extend from neck to back.

The new dinosaur species was discovered in the province of Neuquen, in northern Patagonia, as Bajadasaurus pronuspinax.

The term alludes to the geological formation in which it was found, the Bajada Colorada, and to the long inclined spines that characterize it.

"The neural spines – as they are called – are projections of bone coming out of the upper vertebrae of the neck," said the BBC's Spanish service, paleontologist Pablo Gallina, a researcher at the Felix Azara Foundation's Maimonides University in Buenos Aires and the National Council of Scientific and Technical Investigations of Argentina, Conicet.

"These are very elongated spines and, especially at Bajadasaurus, they have reached a meter or 1.20 m," added Gallina, the lead author of the study in the journal Scientific Reports .

What characteristics did these thorns have and what was their function?

As Antelope Horns & # 39;

The fossils of Bajadasaurus were discovered in 2013 by researchers from the Felix de Azara Foundation and the Ernesto Bachmann Paleontological Museum of Villa El Chocón in Neuquén.

Bajadasaurus belong to the group of herbivorous sauropod dinosaurs, quadrupeds and characterized as being tall and endowed with a long neck and a long tail.

In this group, they were part of the family of dicerosaurs, which were distinguished by their large spines.

In the case of Bajadasaurus, the spines were covered with a reinforcing material.

"We understood that they were formed only bone and maybe the skin was covered only with skin, they would be very fragile and could be broken very easily from the skin. A blow or if the dinosaur was attacked by a predator, "said Gallina.

"They needed an external structure that we compared to what happens, for example, with antelope horns or current goats, where there is a box at the bottom. Outside this keratinous bone. "

Bajadosaurus' closest relative is another dinosaur found in Neuquén, the Amargasaurus, which also had large spines and lived in the area between 15 and 20 million years later.

" In During the appearance of the Amargasaurus, various hypotheses began to be speculated, because these spines attracted much attention.

It has been suggested, for example, that thorns are "a kind of membrane that regulates body temperature, which happens in some reptiles today."

Other researchers have considered the possibility that it was simply a ridge of display based on badual attraction or structures capable of sustaining a hunchbacked to store reserves.

Gallina and his colleagues raise another hypothesis: the function of the spines was defense.

"The explanation we think is very likely is that they were thorns that protruded from the body and had a horn-shaped cover.The presence of this blanket in goats and antelopes leaves grooves in bones, large marks visible in Amargasaurus. "

According to the researcher, it makes more sense that the spectacular display of thorns of these dinosaurs served as an" alert "to hunt predators, in a strategy that he calls "pbadive defense".

"These dinosaurs spent most of the day eating vegetation, they had to be fed continuously, head down, neck leaning forward, leaving thorns exposed as if they were fans. spines pointed forward as a warning sign ".

For Amargosaurus and Bajadasaurus, "it was definitely good to have those thorns that, at first glance, seem to have been very uncomfortable for the animal".

Fossils and the birth of the Andes

Gallina and his colleagues manage to recover 80% of the skull, the best preserved in the world for a dinosaur.

They also extracted from the rocks the first vertebrae of the neck and one of the central parts, in addition to the teeth and jaws.