Miraxis Gegasa newly discovered species of dinosaur with completely disproportionately short arms like T-Rex. Credit: Jorge Gonzalez

Miraxis Gegas – A new species of dinosaur has been discovered with disproportionately short arms just like T-Rex Call Miraxis Gegas.

Dinosaurs (such as the infamous T-Rex) is not the only group of giant carnivorous dinosaurs with small arms. In fact, paleontologists have discovered a new species of dinosaur with completely disproportionately short arms like T-Rex Call Miraxis Gegas. The results are published in the journal current biology Today (July 7), he argued T-Rex And the M Gigas Developed to have small arms completely independently, it identified many potential functions of short arms such as mating or supporting locomotion.

‘fossil M Gigas Never seen before, it shows entire areas of the skeleton, such as the arms and legs that have helped us understand some of the evolutionary trends and anatomy of Carcharodontosaurids – the group that M Gigas It “belongs to,” says Juan Canal, project leader at the Ernesto Bachmann Museum of Paleontology in Neuquén, Argentina.

First, to make things right, the authors say that T-Rex Didn’t get their short arms from M Gigas Or vice versa. Not only M Gigas It became extinct about 20 million years ago T-Rex They became a species, but in the evolutionary tree they are also very far apart. “There is no direct relationship between the two,” Kanal says. Instead, Kanal believes that having tiny arms somehow provides dinosaurs with some kind of survival advantage.

Miraxis Gegas It is a giant carnivorous dinosaur. Credit: Carlos Papulio

“I am convinced that those relatively small arms have some kind of function. The skeleton shows large muscular inserts and fully developed pectorals, so the arm had strong muscles,” Kanall says. This indicates that the arms did not contract because they were useless for dinosaurs. The more difficult question is what exactly are the functions.

From previous studies, the research group has proven that for dinosaurs like M Gigas And the T-RexThe larger their heads were, the smaller their arms became. They certainly weren’t useful for hunting, because “acts related to predation were most likely done by the head,” Kanall argues.

“I tend to think their arms were used for other types of activities,” Kanal says. From the fossil record, the team was able to paint a picture of this life M Gigas before you die. The dinosaur lived in the region of present-day northern Patagonia in Argentina, and was 45 years old, about 11 meters long, and weighed more than four tons. And she had a big family. “The group thrived and reached peak diversity shortly before its extinction,” Kanal says. “They may have used the arms for reproductive behavior such as holding the female during mating or supporting themselves to stand back after a break or a fall,” Kanall adds.

excavation site Miraxis Gegas. Credit: Juan I Canal

The team also found that a skull M Gigas They were decorated with crests, grooves, spurs and small horns. “These motifs appear late in development when individuals become adults,” Kanal says. The group believes that the features may have been used to attract potential mates. “Sexual selection is a powerful evolutionary force. But since we cannot directly observe their behavior, it is impossible to be certain of that,” Kanall says.

“The fossil has a lot of new information in it, and it’s in great shape,” Kanall says. He looks forward to exploring other questions he asks M Gigas Fossil can help him answer. “We found the perfect place on the first day of searching, and M Gigas “It was probably one of the most exciting points of my career,” Kanal says.

Reference: “New Giant Carnivorous Dinosaur Reveals Converging Evolutionary Trends in Theropod Arm Reduction” by Juan I Canal, Sebastian Apisteguia, Pablo A. Galena, Jonathan Mitchell, Nathan D. Smith, Thomas M. Colin, Akiko Shinya, Alejandro Halusa, Federico Giancini, Peter J. Makovsky, July 7, 2022, Available here. current biology.
DOI: 10.1016 / j.cub.2022.05.057

This work was supported by the United States National Science Foundation and the National Geographic Society.