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Five Theropod Lineages Shrank Arms, Gained Strong Skulls

5/26/2026

Summary

UCL Scientists Discover

UCL scientists in the United Kingdom published a study that found forelimb reduction evolved independently in five theropod lineages.
Analysis of 82 species showed short arms correlate more with robust skulls than overall body size.
Using a bite-force, shape and bone-fusion metric, the study ranked Tyrannosaurus rex as having the most robust skull, Tyrannotitan second.
The authors link forelimb loss to an evolutionary arms race with giant herbivorous prey.

Summary

Study Links Arms

A study published May 20 in *Proceedings of the Royal Society B* links skull strength to forelimb size using a metric across five dinosaur groups.
Researchers find that some large predators, such as certain abelisaurs, kept relatively long arms, showing the tiny-armed T. rex was not universal.
The nearly complete T. rex specimen “Trix” at the Naturalis Biodiversity Center in Leiden lets visitors see the diminutive forelimbs the study discusses.

Summary

UCL Researchers Link

Charlie Roger Scherer described forelimb reduction in theropods as a “use it or lose it” process.
Researchers from University College London Earth Sciences and Cambridge University conducted the study, showing cross-institutional collaboration.
Among five lineages, Carnotaurus had forelimbs shorter than Tyrannosaurus rex, illustrating arm-reduction diversity.
The team examined 82 theropod species to link jaw enlargement with arm diminishment.

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UCL Scientists Discover

UCL scientists in the United Kingdom published a study that found forelimb reduction evolved independently in five theropod lineages.
Analysis of 82 species showed short arms correlate more with robust skulls than overall body size.
Using a bite-force, shape and bone-fusion metric, the study ranked Tyrannosaurus rex as having the most robust skull, Tyrannotitan second.
The authors link forelimb loss to an evolutionary arms race with giant herbivorous prey.

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