Why T. rex has little arms

Study finds links in dinosaur anatomy - 1st June 2026

New scientific research has found an explanation for Tyrannosaurus rex's tiny arms. The study was a joint effort by scientists from the University of Cambridge and University College London.

The gigantic T. rex, which lived between 68 and 66 million years ago, measured up to 13 metres in length and could be 4 metres tall. However, its front limbs weren't even a metre long.

Over the years, there have been many attempts to explain their shortness. T. rex might have used them to keep hold of the animals that it ate. Another theory is that they were used to attract a mate.

The research, which was by palaeontologists Charlie Roger Scherer, Paul Upchurch and Elizabeth Steell, studied 85 species. They found that these meat-eating dinosaurs from 5 different lineages all had something in common. The larger the animals they ate, the smaller their arms.

Instead, these huge dinosaurs used their heads to attack their prey. As their skulls were more powerful than their arms, they evolved to be stronger - and their forelimbs shrank. It's a "use it or lose it" scenario, explains Scherer.

The researchers have invented a new way of measuring dinosaur skulls. This allowed them to compare each skull's strength and identified that T. rex had the strongest skull. Tyrannotitan, which lived 30 million years before T. rex, had the second strongest.

This method also identified a clear relationship between dinosaurs having stronger skulls and smaller arms. However, it couldn't say what purpose they had. Scherer's optimistic, stating, "Hopefully, we can find that out with a bit more work."