Overview
- Researchers at UCL and the University of Cambridge analysed cranial and forelimb data for 82 theropod species and published their results this week in Proceedings of the Royal Society B.
- The team introduced a skull 'robusticity' metric that combines bite‑force estimates, skull shape, and how tightly skull bones were joined to measure head strength.
- Across the sample, increased skull robustness correlated more strongly with reduced forelimb length than overall body size or skull length, challenging the idea that tiny arms were just a byproduct of getting bigger.
- Forelimb reduction evolved independently in at least five lineages — tyrannosaurids, abelisaurids, carcharodontosaurids, megalosaurids and ceratosaurids — and different groups shortened arms by different anatomical routes.
- Authors stress the results are correlational, note key examples such as T. rex (highest robusticity), Tyrannotitan (second), Carnotaurus (extreme arm reduction) and Majungasaurus (robust skull at moderate body size), and call for biomechanical and developmental follow‑up work.