New Carnivorous Dinosaur Unearthed in Argentina

Paleontologists have described a new species of large-bodied megaraptoran dinosaur from fossilized remains found in Patagonia, Argentina.

Life reconstruction of Maip macrothorax. Image credit: Agustín Ozán.

The newly-identified dinosaur species lived in what is now Argentina some 70 million years ago (Maastrichtian age of the Cretaceous period).

Scientifically named Maip macrothoraxthe ancient creature was between 9 and 10 m (29.5-32.8 feet) long and weighed up to 5 tons.

It belongs to Megaraptoraa group of theropod dinosaurs known from Gondwana landmasses and Asia.

“Megaraptorans are a group of predatory dinosaurs that inhabited Asia, Australia and South America from Barremian through Maastrichtian times,” said CONICET paleontologist Mauro Aranciaga Rolando and colleagues.

“Most members of this group are known from the Early to Late Cretaceous, with Maastrichtian megaraptorans known only from isolated and poorly informative remains.”

“These theropods are diagnosed by their elongate skulls, the presence of apicobasally short and strongly curved teeth that are 8-shaped in cross section, highly pneumatic axial skeleton reaching to the mid-caudal vertebrae, and long and powerful arms bearing large and sharp manual claws on digits I and II.”

“Although some authors have interpreted megaraptorans as an archaic group of allosauroid theropods, increasing evidence lends support to the hypothesis that they are, instead, members of Coelurosauria.”

“Aside from the consensus currently arrived on the phylogenetic allocation of Megaraptora among Coelurosauria, the internal relations of this group remain poorly resolved.”

The partial skeleton of Maip macrothorax was recovered from the Chorrillo Training in southwestern Santa Cruz Province, Argentina.

The specimen is the most informative megaraptoran dinosaur known from Maastrichtian age.

Maip macrothorax‘s bones helped us better understand the anatomy of megaraptors,” Dr. Rolando said.

“They belong to a family whose skeleton was not like that of a tyrannosaurus — large and heavy — but rather light animals.”

“In other words, their bones were not solid, but rather had a large number of internal voids that made them much lighter, something like a hollow brick compared to a solid one.”

“Besides, they had long tails and long legs, which also corroborates that they were relatively agile animals.”

“The most characteristic of these dinosaurs are their arms: long, gigantic, topped by claws up to 35 cm (13.8 inches) long, with which we infer that they grabbed and tore their victims to pieces.”

“They were their main weapon, as their teeth were sharp but small.”

According to the researchers, Maip macrothorax and other South American megaraptorans belong to a monophyletic group, whereas Australian and Asian members constitute successive stem groups.

“South American forms differ from more basal megaraptorans in several anatomical features and in being much larger and more robustly built,” they said.

The discovery of Maip macrothorax is described in a paper in the newspaper Scientific Reports.

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AM Aranciaga Rolando et al. 2022. A large Megaraptoridae (Theropoda: Coelurosauria) from Upper Cretaceous (Maastrichtian) of Patagonia, Argentina. Sci-Rep 12, 6318; doi: 10.1038/s41598-022-09272-z

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