Maip: the huge carnivorous predator that was one of the last dinosaurs before extinction

CONICET scientists published its discovery in Scientific Reports.

A CONICET research team at the Argentine Museum of Natural Sciences “Bernardino Rivadavia” (MACN) discovered the bones of the largest megaraptor known to date in the province of Santa Cruz. It is estimated that this carnivorous specimen, in whose discovery two paleontologists from Japan also participated, would have lived in Patagonia in the time before the extinction of the dinosaurs, the so-called Cretaceous Period, almost seventy million years ago. The discovery of this species, which was baptized with the name Maip due to its characteristics, has just been published in Scientific Reports.

“With Maip we beat the pandemic,” says CONICET paleontologist Fernando Novas, head of the ‘Laboratorio de Anatomía Comparada del MACN and leader of the team that collected Maip’s bones near El Calafate days before the global pandemic broke out due to the Coronavirus, in mid-March 2020. Once compulsory social and preventive isolation was decreed, the team of thirty paleontologists and technicians who were in the middle of a research expedition in the area had to interrupt their homework. They were isolated in El Calafate, 2,700 kilometers from Buenos Aires, until they were able to return. Back at home, they divided up the samples collected in the field and continued with the process of preparing the fossils and their subsequent study. “Although the pandemic prevented us from returning to our workplace, we managed to continue with the study of Maip’s morphological traits,” says Novas proudly.

The characteristics of this new dinosaur were very novel: Maip was between nine and ten meters long and weighed approximately five tons. To support this weight, its spine was made up of huge vertebrae interconnected by a complex system of muscles, tendons and ligaments, which the team was able to reconstruct from observing a series of ridges and grooves in its joint regions. That system allowed the animal to stand upright on its hind legs while walking or running.

“Maip’s bones helped us better understand the anatomy of megaraptors. 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”, explains CONICET fellow Mauro Aranciaga Rolando, first author of the article. 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 thirty-five centimeters 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.

Paleontologists already had some information about the megaraptor family: the first of the finds of this group of dinosaurs was Megaraptor naumunhuaiiquii, discovered in 1996 by Novas in the province of Neuquén, which was followed by the discoveries of new megaraptors in Australia, Japan and Thailand. “When I found the first megaraptor in Neuquén, it was a big shock”, recalls Novas, “because it was an enormous carnivore that had hands with claws about forty centimeters long. Something never seen before. Smaller relatives of this species were later discovered in Australia. Then also in other regions of Patagonia so the family of these dangerous predators expanded. These findings are completed with Maip: now we have one of the largest, most robust and one of the last to live in the area before the mass extinction at the end of the Cretaceous”, warns the scientist.

Maip’s name was chosen by Aranciaga Rolando. The choice had to do with the fact that “it comes from an evil being from Tehuelche mythology who lived in the mountains and killed using the cold. Precisely, Maip’s finding took place in south El Calafate, from where the lavish Cordillera de los Andes can be seen, a place with very cold temperatures. Besides, for the Tehuelches, Maip represented the shadow that death leaves in its wake, while we imagine that during the Cretaceous, this great predator with its enormous size would have caused something similar,” explains the fellow. The term macrothorax refers to the enormous thoracic cavity that this dinosaur possessed.

Maip was found in a very particular area: Estancia La Anita, located a few kilometers from El Calafate. A territory that seventy million years ago was a warm ecosystem: there were aquatic and terrestrial snails, plants of very different affiliation, it was a forest, almost a jungle, with puddles, lakes, streams, and diverse creatures such as frogs, turtles, fish, small birds, and mammals. The Andes mountain range had not yet risen. From all those organisms that lived at that time, we were collecting fossil remains, and now, with Maip, we have added a super predator that completes the food pyramid.”

This place, which was so different seventy years ago, was a dreamscape for the research team. “When we are on a campaign, the paleontologist’s office is moved temporarily to a beautiful place, and this was the case,” Aranciaga Rolando comments. “Today it is a place surrounded by huge mountains, glaciers, lakes, which demands that we have to walk for many hours in extreme weather conditions. However, being there, while we were digging to get out this dinosaur that was buried seventy million years ago, we felt incredibly happy. It is a place that today has an extraordinary view, a landscape worthy of  a Lord of Rings movie. From the top of the ridge, one can see the Pedrito Moreno Glacier, and different mountain peaks such as Torres del Paine or El Chaltén. And this site is a privileged place because it allows us to know better the different members of that ecosystem that developed south of El Calafate. It is a fossil treasure that we are just beginning to discover and understand.”

Although Maip’s skeleton provides a lot of information, there are still many unanswered questions. “We still don’t know several parts of the skeleton of this animal, such as the skull and the arms, that’s why we plan to return to the plae to look for more fossils,” affirms Novas. For his part, Aranciaga Rolando adds that “megaraptors are quite enigmatic predators, and although Maip helped us tie up several loose ends -especially their kinship relationships with other carnivorous dinosaurs-, aspects of their hunting behavior still remain to be elucidated; for instance, what would have been their favorite prey, among other things.” To answer these questions, paleontologists are already planning a next expedition, which they hope to complete in early 2023 to collect more data on these ancient inhabitants of southern Patagonia.

Research team:

Mauro Aranciaga Rolando, CONICET doctoral fellow at the MACN

Matías Motta, CONICET doctoral fellow at the MACN

Federico Agnolín, CONICET researcher at the MACN

Fernando Novas, CONICET researcher at the MACN

Makoto Manabe, scientist of the National Museum of Nature and Science in Tokio

Takanobu Tsuihiji, scientist of the National Museum of Nature and Science in Tokio

By Cintia Kemelmajer