After 60 million years, we now know why the T-Rex had tiny arms

If we had to decide which is the most famous dinosaur of the entire Cretaceous, we would undoubtedly say that the Tyrannosaurus rex. His fearsome appearance is only out of tune because of those two little arms that come out of his chest. Now we could know the reason for these.

If you have seen Jurassic Park or Jurassic World, surely the figure of the T-Rex sounds familiar to you. He is not only the undisputed protagonist of the first film (and always present in both trilogies) but he is also the logo of all of them. Yes, that logo you have engraved on your head.

The point is that, despite being very famous in the world of paleontology, there were big questions around him. Among them, the doubt about the origin of his little arms was the most striking. At least for the rest.

Paleontologists have described a new species of giant carnivorous dinosaur from a fairly complete skeleton in Patagonia. The discovery could help shed new light on the mystery of why such powerful predators had tiny arms.

The new species has been named What Meraxes gigas, with the first part referring to a dragon from the A Song of Ice and Fire novels by George RR Martin and the second part from the Greek word for “giant”.

And gigantic it was: the dinosaur weighed more than 4 tons, was almost 11 m tall and had a huge skull 1.3 m long. That head was adorned with a series of ridges, bumps, grooves, and horns, giving it a fearsome appearance.

But one thing about this new species wasn’t so giant: its arms. Like many carnivorous theropods, its forelimbs were disproportionately small, measuring less than half the length of his femur.

This means that Meraxes could not reach its mouth, so it is unlikely that the arms were used for anything related to feeding. PBut if that’s the case, what was he using them for?

That’s a question paleontologists have pondered for decades, and many have hypothesized that these are vestigial limbsevolutionary remnants that are reduced over time when animals no longer need them. But the newly discovered skeleton suggests otherwise.

“I am convinced that those proportionately small arms had some kind of function. The skeleton shows large muscle insertions and fully developed pectoral girdles, so the arm had strong muscles.“, explains Juan Canale, project manager at the studio.

The researchers propose other possible uses for these arms, such as helping the huge animal get up from the ground after a rest., or to hold your partner during mating. This coincides with suggestions from other scientists in the past.

Whatever the function, it must have been important, because the new study shows that small forelimbs evolved multiple times in at least three different lineages.

And they are not direct ancestors of each other either. Meraxes lived about 95 million years ago and went extinct about 20 million years before the T-rex evolved.

We may not have definitive answers, but surely someone has taken notes for the next Jurassic World movie. We are looking forward to it. Although the same idea is copied by the villain of our time, Elon Musk.