Why did T. rex have tiny arms? Scientists now think they know why
Scientists have proposed a new explanation for the small arms of Tyrannosaurus rex, suggesting they are a result of evolutionary trade-offs. A study analyzed 85 dinosaur species and found that larger skulls correlated with smaller forelimbs. This research adds statistical support to the idea that as dinosaurs evolved stronger skulls for hunting, their forelimbs became less necessary and shrank over time.
- ▪The arms of T. rex were less than a third of the length of its legs.
- ▪A new study published in the journal Proceedings of the Royal Society B concluded that tiny arms were an evolutionary trade-off for larger skulls.
- ▪The research found a correlation between large skulls and small forelimbs in five different groups of dinosaurs.
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| Original publisher | CNN |
| Canonical URL | https://www.cnn.com/2026/05/25/science/t-rex-tiny-arms-function |
| Publication time | Mon, 25 May 2026 16:00:34 +0000 |
| Retrieval time | 2026-05-25T16:07:38.273Z |
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window.CNN.contentModel.leadingMediaType = 'image'; window.CNN.contentModel.isVideoCollection = false; Animal stories Ancient creatures See all topics Facebook Tweet Email Link Threads Link Copied! Follow Scientists may have finally solved the riddle of Tyrannosaurus rex’s small arms, which have always stood out as the oddest feature in the mightiest of dinosaurs, prompting jokes and a century-plus debate on their purpose and evolutionary history. At about 3 feet long, the arms of T. rex were less than a third of the length of the dinosaur’s legs and looked noticeably disproportionate in a body that could span more than 40 feet in larger adults. T.
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