Why did the Tyrannosaurus rex have such short arms? A new theory has emerged that suggests it might have been for defense during feeding frenzies.

Driving the news: Scientists recently theorized in a new study published in the journal Acta Palaeontologia Polonica that the T. rex might have evolved to become shorter to reduce the chance of losing its arms during feeding frenzies.

Behind the lines: The study suggests that tyrannosaurids may have hunted in packs.

  • If these dinosaurs hunted together, then it would mean a slew of T. rexes were eating and hunting at the same time.
  • The massive jaws and sharp teeth would then pose a threat to each fellow dinosaur in the pack.

What they’re 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,” Kevin Padian, professor of integrative biology and curator at the University of California’s Museum of Paleontology, told Berkeley News.

  • “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.”
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Yes, but: Padian admitted that his own research does not explain how the arms got shorter, only that the arms were possibly shorter because of evolution, according to IGN.

  • He said he could strengthen his own theory by looking at fossil bite marks to see if there’s a connection.
  • He said it will be hard to figure this out, though, since the T. rex has been extinct for 66 million years, per SlashGear.