A paleontologist at the University of California, Berkeley puts forward a new theory as to why T. Rexes had such small arms

Lots and lots of kids and adults wondered out loud when first getting to know the dinosaur king Tyrannosaurus RexWhy did these powerful extinct beasts have short and short little arms. Well, a UC Berkeley professor has a new answer.

Kevin Badian, distinguished professor emeritus of integrative biology at the University of California, Berkeley, and curator of the University of California Museum of Paleontology (UCMP), believes that until now paleontologists have been taking the short arm issue all wrong. Evolutionarily speaking, Badian believes, it might be a mistake to think about what those short arms evolved for, but rather what they evolved to get out of the way.

as UC Berkeley News reportsThe new Badian theory was published in Acta Paleontology Paulonica, And it goes like this: What if dinosaurs with shorter forelimbs had a biological advantage over their longer-armed counterparts when it came to how they fed the animals?

“What if several adult dinosaurs converged on a carcass? You have a set of huge skulls, with incredibly strong jaws and teeth, tearing flesh and bone right next to you. What if your friend thinks you’re getting a little too soon? He might warn you away by cutting your arm off,” Badian explains. “So it may be beneficial to reduce the forelimbs, because you’re not using them for predation anyway.”

All previous hypotheses about the cause T-Rex Having only such short arms, Badian says, could explain why they have kept those short arms for generations. Among the theories are that it was somehow useful in mating, or that they used it in coup d’etat Triceratops.

He says the Badian theory explains why there are ancestors T-Rex They have longer arms, and why evolution shortened them T-Rex and similar species around the world.

Notes that a dinosaur People who have just had their arm cut off are likely to die quickly from bleeding, shock, or possible infection. So the surviving T-Rexes Those with shorter forelimbs were more successful and more able to spread.

Only in recent years has fossil evidence led to this belief Tyrannosaurus Rex It was a herd animal, and it is likely that it was hunted and fed in groups. This idea led Badian directly to the new hypothesis.

“Several important quarry sites discovered in the last 20 years preserve both adult and juvenile dinosaurs,” Badia told UC Berkeley News. “We can’t really assume that they lived together or even died together. We only know that they were buried together. But when You find several sites with the same animals, that’s a stronger signal. The possibility, already put forward by other researchers, is that they were hunting in groups.”

Badian says that more tests of the short arm theory will be needed, and that will require some kind of crowdsourcing.

“Bite wounds on the skull and other parts of the skeleton are well known in tyrannosaurus and other carnivorous dinosaurs,” Badian said. “If fewer bite marks are found on the miniature limbs, it may be a sign of the reduction’s success.”

Photo: Marcus Spaceki