A fossil of Giga Meraxes, as the new dinosaur has been called, was found in the present-day region of northern Patagonia, Argentina, revealing that the creature was 11 meters (36 feet) long and weighed more than four tons, according to a study. published Thursday in the journal Current Biology.
At the time, the area would have been warm and humid with many watercourses and vegetation, including large trees, Juan Canale, the project manager at the Ernesto Bachmann Paleontological Museum in Neuquén, Argentina, told CNN.
The carnivore is from the group of dinosaurs Carcharodontosauridae, which lived in the Cretaceous period, between 145 and 66 million years ago, according to the study.
A fossil pond of Carcharodontosauridae has been found in the last 30 years, but little is known about its skull, forearms or feet.
This has changed with the discovery of M. gigas, thanks to the remarkably complete fossil.
“For the first time we know, in great detail, certain parts of the anatomy of these giant carnivorous dinosaurs,” Canale said.
The researchers found an almost complete anterior limb, which allowed them to conclude that M. gigas had tiny arms for such a large dinosaur, a physical feature shared with T. rex that has long baffled paleontologists.
They also found an almost complete skull and foot, which allowed them to shed light on how this group of dinosaurs evolved, Canale said, explaining that there was a trend toward larger body sizes, larger skulls and more arms. small in proportion to the body.
“There was a kind of arms race”
The fossil was found in the Huincul Formation, where the study said remains of one of the largest known terrestrial animals of all time, Argentinosaurus huinculensis, have been found, dating from the same period as the M fossil. gigas.
It is also known that the area was home to other carnivorous dinosaurs, although smaller than M. gigas, as well as other long-necked herbivorous species.
Canale said it is generally very difficult to establish what dinosaurs ate, but loose teeth found at excavation sites where herbivorous dinosaur fossils have been discovered have been linked to carnivorous dinosaurs.
This means that we can say that M. gigas would have preyed, at least in part, on these long-necked herbivores such as Argentinosaurus huinculensis, he added.
“It’s no coincidence that giant herbivorous dinosaurs and giant carnivorous dinosaurs live in the same environments,” said Canale, who explained that as herbivores evolved larger bodies as a form of defense, carnivores also did so. do to be able to prey on them.
“There was a kind of arms race,” he said.
‘No direct relationship’ with T. rex
But the team says M. gigas evolved separately into T. rex and became extinct nearly 20 million years before T. rex walked the earth.
Canale said that while the two dinosaurs had large heads and small arms, their bone structure is very different.
“There’s no direct relationship,” Canale said.
M. gigas ’ancestors had longer arms and smaller heads and their arms would have been important in hunting, Canale said, but that changed over time.
Previous research found that dinosaur species such as M. gigas and T. rex developed smaller arms as their heads grew larger.
This shows that the weapons were not used for hunting, but used the head to kill their prey, Canale said.
“What I think is that, in the most evolved forms … activities related to predation, such as catching or holding prey, would have been done right away with the head,” he said.
However, the fossil shows that while the arms were short, they were muscular and the chest muscles were also well developed, Canale said.
“This is not consistent with a limb that has no function,” he said, adding that they could have been used to help lift off the ground, or as a support to the female during mating. Researchers do not know if this fossil belonged to a male or female dinosaur.
The team also found that M. gigas had ornamentations such as ridges, furrows, bumps, and small horns on the skull, which were probably used to attract potential mates.
There is still more work to be done on M. gigas, Canale said, and a colleague at the museum is writing a thesis on his feet and arms.
In addition, there are many fossils that have yet to be excavated in the area, as well as dinosaur footprints for analysis, he said.
“We have a lot of work ahead of us,” Canale added.