The massive and fearsome Tyrannosaurus Rex may be the most recognizable dinosaur of all time, but it has long been the butt of jokes due to its tiny, seemingly pointless arms. But according to one paleontologist, there may have been an important evolutionary purpose behind the reptile’s stubby forelimbs.
In a new study published in Acta Palaeontologia Polonica, Kevin Padian, professor of integrative biology and curator at the University of California’s Museum of Paleontology, theorizes that the T-Rex’s arms evolved to be short so as to reduce the chances of accidental dismemberment during feeding frenzies.
While it’s often assumed that tyrannosaurids hunted solo, more recent evidence indicates that many of them may actually have hunted in packs. That being said, when it came to feeding time, the animal’s humongous jaws and razor-sharp teeth could do some pretty serious damage to anything caught in its path.
Padian suggests in his report that “during group-feeding on carcasses, limb reduction was selected to keep the forelimbs out of the way of the jaws of large conspecific predators, avoiding injury, loss of blood, amputation, infection, and death.”
Speaking to Berkeley News, Padian elaborated on his hypothesis, saying, “What if several adult tyrannosaurs converged on a carcass? You have a bunch of massive skulls, with incredibly powerful jaws and teeth, ripping and chomping down flesh and bone right next to you. What if your friend there thinks you’re getting a little too close? They might warn you away by severing your arm. So, it could be a benefit to reduce the forelimbs, since you’re not using them in predation anyway.”
For many years, it was assumed that the T-Rex’s tiny arms were merely an evolutionary holdover, much like a human’s wisdom teeth or the wings on certain species of flightless birds. Over the years, however, some paleontologists have begun to theorize that the T-Rex’s short forelimbs could also have evolved to aid them in tipping over other large dinosaurs, holding a mate in place, or gnashing at prey in close-quarters.
Although he doesn’t presume that his new hypothesis is the final word on anything, Padian is also unconvinced that any previous suggestions are viable, stating that they are “untested or impossible because they can’t work.”
“And none of the hypotheses explain why the arms would get smaller,” he said. “The best they could do is explain why they would maintain the small size. And in every case, all of the proposed functions would have been much more effective if the arms had not been reduced.”
Padian expects that he can strengthen his theory greatly by studying fossil bite marks in existing specimens in museums across the globe.
It’s not the only T-Rex theory we’ve heard recently – some scientists now posit that T-Rex was actually three different species. As for the rest of us, we’ll probably be doing most of our T-Rex research by watching Jurassic World Dominion later this year.
Billy Givens is a freelance writer at IGN.
