Tyrannosaurus Rex and Other Terrifying Predatory Dinosaurs Had Itty-Bitty Arms. Scientists May Have Finally Figured Out Why
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A new study has revealed that the tiny arms of theropod dinosaurs like Tyrannosaurus rex may be an evolutionary trade-off for their powerful jaws and skulls. Researchers found a strong correlation between skull strength and forelimb size among various theropod species. This suggests that as these predators evolved to tackle larger prey, their forelimbs became less necessary.
- ▪The study published in Proceedings of the Royal Society B suggests that smaller forelimbs in theropods are linked to stronger skulls.
- ▪T. rex had arms that were only about three feet long, significantly smaller than its legs.
- ▪The research analyzed 85 non-avian theropod species to establish the relationship between skull strength and forelimb size.
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Tyrannosaurus Rex and Other Terrifying Predatory Dinosaurs Had Itty-Bitty Arms. Scientists May Have Finally Figured Out Why A new study suggests that certain theropods—two-legged, mostly meat-eating dinosaurs—had shrunken forelimbs as an evolutionary trade-off for their strong skulls Sara Hashemi | Daily Correspondent May 29, 2026 11:53 a.m. ShareCopy linkEmailSMSFacebookXRedditLinkedInBlueskyPrintAdd as preferred source Researchers weren't sure what drove some theropods, like T. rex, to evolve tiny arms relative to their body sizes. Alex Segre / UCG / Universal Images Group via Getty Images Tyrannosaurus rex’s tiny arms might seem out of place on a massive predator, but there must have been an evolutionary reason for the limbs’ almost comical size.
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Excerpt limited to ~120 words for fair-use compliance. The full article is at Smithsonian Magazine.
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