Mystery of T-Rex's tiny arms may have been solved

Meat-eating dinosaurs such as Tyrannosaurus rex evolved small forelimbs linked to the development of large, powerful skulls and jaws. Data from 82 species showed smaller arms were closely associated with stronger cranial and jaw features. Researchers propose that hunting shifted toward using jaws and heads rather than claws, especially when giant sauropods became prey. Pulling and grabbing a very large sauropod with claws would be ineffective, while attacking and holding with jaws could be more successful. Strong skulls likely evolved before shorter forelimbs, since losing an attack mechanism without a replacement would not be evolutionarily sensible. Forelimbs then became less useful and reduced over time, with some theropods developing even smaller arms.

"Experts at University College London (UCL) and the University of Cambridge studied data from 82 species and found smaller arms were closely linked to the development of large, powerful skulls and jaws. The researchers believe that the evolution of gigantic sauropods may have resulted in a shift to hunting using jaws and heads instead of claws. Many of the giant theropod dinosaurs also evolved small forelimbs, with the Carnotaurus having arms even smaller than those of the T-Rex."

"Charlie Roger Scherer, a PhD student at UCL Earth Sciences, said: "Trying to pull and grab at a 100ft-long sauropod with your claws is not ideal. Attacking and holding on with the jaws might have been more effective. "It is highly likely that strongly built skulls came before shorter forelimbs. It would not make evolutionary sense for it to occur the other way round, and for these predators to give up their attack mechanism without having a back-up.""

"Mr Scherer added: "It's a case of 'use it or lose it' - the arms are no longer useful and reduce in size over time." Researchers found the evolution of small arms mostly occurred in areas where large prey roamed. They believe that the head gradually took over from the arms as the prime method of attack. The team developed a new way to quantify skull robustness, based on factors including how tightly"

Read at Irish Independent