A new species of armless dinosaur discovered in Argentina belongs to a family of fearsome predators

• Paleontologists discovered a new species of armless, carnivorous dinosaur in Argentina.
• Unlike other members of the abelisaurid family, this dinosaur had holes in its skull and no horns.

Paleontologists unearthed a 70-million-year-old dinosaur skull in Argentina and discovered a new species of armless hunter.

The new dinosaur, called Guemesia ochoai, is an abelisaurid — a family of top-tier predators that roamed the lands that are now South America, Africa, and India. Scientists think they preyed on some of the largest dinosaurs that ever lived, like the titanosaur, a 70-ton herbivore larger than a blue whale.

Abelisaurids were powerful hunters without using their arms. The appendages were remarkably short, even smaller than those of T. rex, and effectively useless. Instead, the fearsome carnivores relied on their powerful heads and jaws to hunt.

The new dinosaur's cranium was discovered in the red siltstone of the Los Blanquitos Formation in northwest Argentina.

Unlike other abelisaurids, the new fossil has holes in the front of its skull, which could have helped the dinosaur release heat to cool down. It has no horns, which are a signature feature of other abelisaurids. These distinctions could mean that Guemesia ochoai is one of the first species of abelisaurid to ever evolve, or is closely related to such an ancestor.

"This new dinosaur is quite unusual for its kind. It has several key characteristics that suggest that is a new species, providing important new information about an area of the world which we don't know a lot about," Anjali Goswami, who leads research at the UK Natural History Museum and co-authored the discovery, said in a press release.

"It shows that the dinosaurs that live in this region were quite different from those in other parts of Argentina," she added.

Argentina was a major abelisaurid stomping ground: 35 species of the armless carnivores have been discovered there, mostly in the southern Patagonia region.

The new dino finding, published this month in the Journal of Vertebrate Palaeontology, suggests that northwestern Argentina may have been home to unique creatures in the late Cretaceous period, just before an asteroid impact wiped out the dinosaurs 66 million years ago.

Goswami's team has uncovered several other new species at the same dig site, including fish and mammals. They're still in the process of describing them in papers for publication.

"Understanding huge global events like a mass extinction requires global datasets, but there are lots of parts of the world that have not been studied in detail, and tons of fossils remaining to be discovered," Goswami said.