Chakisaurus Nekul, a previously unknown dinosaur that lived almost 100 million years ago

In the arid territory of El Chocón, in the Argentine province of Río Negro, the land holds the secrets of a past inhabited by dinosaurs and other animals.

The team of Argentine paleontologists from the Laboratory of Comparative Anatomy and Evolution of Vertebrates (LACEV) and the “Félix de Azara” Natural History Foundation, belonging to the National Council of Scientific and Technical Research (CONICET), in Argentina, year after year undertake the tireless search for information about these prehistoric species. The results of their work reveal fragments of the Earth’s fascinating biological history.

The most recent of these discoveries is a herbivorous dinosaur, named Chakisaurus nekul, and whose discovery was made in the 2018 campaign in the Pueblo Blanco Natural Reserve, an expedition that had the support of National Geographic. The long research has allowed us to determine the characteristics of this animal.

“It is estimated that the largest Chakisaurus individual reached 2.5 or 3 meters long and 70 centimeters high. The other specimen, smaller, was much smaller in size, barely reaching 1 meter in length,” explains Federico Agnolín, member of LACEV, to the CTyS-UNLaM Agency.

Its name derives from Chaki, which in the Aonikenk language of the Tehuelche people means “old guanaco.” “The choice is made because, aside from the obvious differences, both animals would have shared a similar ecological niche. Both were medium-sized herbivores, good runners, and could be prey to the supreme predator in their area. Nekul, on the other hand, means ‘fast’ or ‘agile’ in the Mapudungún language, of the Mapuche people,” paleontologist Rodrigo Álvarez Nogueira from LACEV, who also heads the work, told the CTyS-UNLaM Agency.

During the campaign, bones of several individuals of different sizes were found, mostly corresponding to the spine and limbs. Their study indicated that it was undoubtedly within the group known as Elasmaria, which includes medium- to small-sized herbivorous dinosaurs, and whose knowledge began to flourish in recent years.

A moment in paleontological research. (Photo: LACEV / Félix de Azara Natural History Foundation / CONICET / CTyS-UNLaM Agency)

Chakisaurus, researchers say, is known mainly from the vertebrae of the spine and the bones of the forelimbs and hindlimbs. The vertebrae, most of which correspond to the tail, are a very little-known part of these animals. The studies provide very novel data, such as characteristics that indicate that Chakisaurus was a fast runner and that, unlike other dinosaurs, it had its tail curved downwards. “More expeditions need to be carried out to confirm that this orientation really existed,” Agnolín clarified, “but if so, it would mean a great discovery for vertebrate paleontology.”

In addition, the team found a humerus in perfect condition, only 9 centimeters long and belonging to a still young individual. “This bone was very useful for making comparisons with other dinosaurs in the group, and making inferences about their habits,” stressed Álvarez Nogueira. “Now we know that, within the group, there were animals with different types of locomotion: from some, generally smaller, completely bipedal, such as Chakisaurus, to others of larger size that could probably vary between moving with two or four limbs,” he adds.

For most of the history of paleontology in Argentina and South America, saurischian dinosaurs (long-necked herbivores and carnivores) largely dominated the record. But in recent decades, ornithischian dinosaurs, including Chakisaurus, have begun to be increasingly frequent in paleontological expeditions. “Thanks to this, it is now known that these animals were much more common in the Patagonian fauna than previously thought,” says Agnolín.

This pioneering study has been published in the academic journal Cretaceous Research. (Source: Magalí de Diego / CTyS-UNLaM Agency)