Study Links T. rex Arm Size to Skull Growth Across Five Dinosaur Groups

A Royal Society research paper published May 20 examined 85 dinosaur species and reported a consistent pattern among five predatory groups in which skull size increased while forelimb length decreased. The groups identified were Tyrannosaurus, ceratosaurids, megalosaurids, abelisaurids and carcharodontosaurids. T. rex averaged more than 40 feet in length with forelimbs of about 3 feet.

The study states that as prey animals grew larger, these dinosaurs relied more on powerful jaws. Lead author Charlie Roger Scherer, a doctoral student at University College London, said the head became the primary contact point with prey. Scherer told CNN that evolution reduced investment in forelimbs once the skull took over the main predatory function.

The paper noted that forelimb reduction occurred at different rates across species.

Scherer added that the arms were not eliminated entirely. “They obviously served some kind of function, otherwise they wouldn’t have them,” he said. Vertebrate paleontologist Stephan Lautenschlager of the University of Birmingham told CNN that large herbivorous dinosaurs did not show the same reduction and kept longer forelimbs, possibly for grasping vegetation or defense. T.

rex is described as Earth’s largest known land predator, reaching lengths over 40 feet, weighing 8 to 14 tons, and exerting bite forces above 12,000 pounds. It inhabited western North America until an asteroid impact 66 million years ago.