One study suggests that the T. Rex may have evolved its small arms to help it rise again after falling.
Although it was probably the fiercest terrestrial predator of all time, equipped with 60 eight-inch-long serrated teeth and an overwhelming bite, the Tyrannosaurus Rex has been mocked in the modern world for its small forelimbs, which measure only three feet long and serve. no clear purpose.
But the discovery of a new dinosaur, which also had disproportionately small arms, shows that the tiny limbs of the T. Rex may have been really beneficial and played a very important role.
Meraxes gigas is a species that resembles T. rex, although it became extinct 20 million years before it existed. The discovery of a new fossil of M. gigas in Patagonia reveals that both species have a huge head, sharp teeth, a long tail, weigh several tons and, apparently, tiny arms.
Convergent evolution
But the two creatures are not even remotely related, occupying opposite branches of the dinosaur evolutionary tree.
This, experts say, is an example of convergent evolution, where two species evolve independently the same trait and only happens if it has a clear and significant survival advantage.
“I’m convinced that those proportionately small arms had some kind of function. The skeleton shows large muscle insertions and fully developed pectoral fissures, so the arm had strong muscles,” says Juan Canale, the lead researcher on the excavation project. of M. gigas from the Ernesto Bachmann Paleontological Museum in Neuquén, Argentina.
One thing they were almost certainly not used to was hunting, he said, as the huge muscular head full of dozens of dagger-like teeth was more than enough to grab food.
He may have used arms for reproductive behavior
“I tend to think his arms were used in other types of activities,” Canale said.
“They may have used their arms for reproductive behavior, such as holding the female during mating or leaning to stand up after a pause or fall.”
The authors, writing in the journal Cell Press, also suggest that short limbs could be part of an evolutionary exchange agreement. Resources can be invested in long limbs or in a large head, but not in both.
Thus, there are dinosaurs with long limbs and small heads and creatures with large heads and short arms. However, there cannot be one with both, the researchers suggest.
“The presence of multi-toned theropods with long forelimbs, but small skulls, further confirms that the reduction of the forelimbs is not a simple function of the body size of the theropods, but tracks some other trait, which for large predatory species is probably the size of the skull., “they write.