Tyrannosaurus Rex and Other Terrifying Predatory Dinosaurs Had Itty-Bitty Arms. Scientists May Have Finally Figured Out Why

Sara Hashemi· May 29, 2026 · 3:53 PM UTC ·4 min read · 0 reactions · 0 comments · 41 views

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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.

Key facts

▪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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Smithsonian Magazine · Sara Hashemi

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Canonical URL	https://www.smithsonianmag.com/smart-news/tyrannosaurus-rex-and-other-terrifying-predatory-dinosaurs-had-itty-bitty-arms-scientists-may-have-finally-figured-out-why-180988803/
Publication time	Fri, 29 May 2026 15:53:48 +0000
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Opening excerpt (first ~120 words) tap to expand

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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