Why Did T-Rex Have Small Arms? The Evolutionary Explanation

Jakarta –

Tyrannosaurus rex or T-rex is known as the most ferocious dinosaur and has the strongest bite among all animals that have ever walked on land. However, judging from its shape, T-rex has very small hands compared to its body. Why?

Despite being extinct, T-rex is known to have lived in the wilderness at the end of the Cretaceous, more than 66 million years ago. This T-rex could prey on Triceratops or Edmontosaurus.

Even though it was a terrible predator, it had the characteristic tiny arms that its theropod relatives, or groups of meat-eating dinosaurs that walked on two legs, also had this feature.

Not Biting Each Other

Launch page Live ScienceHowever, it turns out that bone-crushing theropods like T-rex evolved small arms so they wouldn’t bite each other’s arms while they ate.

This was revealed through a study in 2021, which was published in the journal Acta Paleontologica Polonica.

Through paleontological evidence, it is known that this group of animals will eat their prey in groups.

So it has been hypothesized that they evolved with tiny arms to avoid accidentally tearing the arms apart when a group of theropods charged over a captured Triceratops.

“It’s a good story,” said John Hutchinson, a biologist from the Royal Veterinary College, University of London, who was not involved in the study.

“But I think, in the end, we don’t really know,” he added.

Enlarged Feet

Through Hutchinson’s study of the biomechanics of movement of large land animals, both living and extinct, he is looking at the evolution of the forelimbs of dinosaurs quite differently.

Hutchinson said the T-rex’s arms didn’t get shorter, but its legs got longer.

“As animals got bigger, the forelimbs got smaller and the heads got bigger,” explains Hutchinson.

“(Tyrannosaurs, in particular), adapted to the bone-crushing killer bite to their head, so they specialized their head very much and then they really, really reduced their forelimbs,” he added.

Use the Head to Kill the Victim

As tyrannosaurs and other theropods evolved with larger heads and bipedal postures, they used their forelimbs less.

T-rex will mostly use their heads to catch and kill prey. It caused the forelimbs to not grow as much as the rest of their bodies.

“Animals can only use part of their body volume for one thing or another. They can’t be good at everything,” says Hutchinson.

The T-rex’s tiny arms rendered them unusable in hunting and killing.

This giant dinosaur used a ‘stab-pull’ method of dropping prey, in which the T-rex would bite large chunks off its prey and then rip backwards with its powerful neck.

The way T-rex hunted turned out to be similar to how the Komodo dragon (Varanus komodoensis) hunts today.

On the other hand, the T-rex’s large hind legs will help them maintain their body balance. Unfortunately, until now there is no evidence that his small arms help in any way.

Sometimes traits belonging to an animal that play a role in its evolution just appear and disappear without conferring any obvious evolutionary benefit. In this case, the feature is the T-rex’s small arms that haven’t changed like the rest of its body.

The rest of the T-rex’s body grew to colossal sizes to help them survive in their environment. There was probably no need for the arms to grow along with the T-rex’s body, thus making him look very small compared to the rest of his body.

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2023-06-28 11:00:00
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