New research suggests that the short arms of the Tyrannosaurus rex may have evolved to reduce the risk of injury while hunting.
T. rex is perhaps the most famous dinosaur, but for many years, scientists have struggled to provide a definitive answer to an important question about its anatomy: why are its two arms, or forelimbs, so short?
An adult T. rex measuring 13.7 meters long could have a skull up to 1.5 meters in length, yet its arms were only 90 centimeters long. This is akin to a person standing 1.8 meters tall having arms just 12.7 centimeters long.
Simulation of Tyrannosaurus rex. (Photo: Warpaint)
The ancestors of T. rex are believed to have had smaller bodies but larger forelimbs. This suggests that the reduction in arm size later on must have had some rationale. Previous studies speculated that short arms helped T. rex grip prey better and facilitated mating, but a new report in the journal Acta Palaeontologia Polonica last week presented an entirely different hypothesis from paleontologists at the University of California, Berkeley (UC Berkeley).
The research team believes that the forelimbs of T. rex shrank in length to reduce the risk of being bitten off—either accidentally or intentionally—by its own kind during attacks and dismemberment of prey.
“What would happen if multiple adult T. rexes were competing over a carcass? You would have a series of enormous skulls, with extremely powerful teeth easily capable of tearing flesh and crushing bones. If a T. rex felt another was too close while vying for food, it might bite the opponent’s arm as a warning. Thus, the reduction in forelimb size is advantageous in this situation, especially since T. rex didn’t use them for hunting,” explained Professor Kevin Padian from UC Berkeley, the lead author of the study.
A bite from a T. rex could easily sever a rival’s arm, leading to infection, hemorrhaging, shock, and ultimately death.
In the next phase of research, Padian and his colleagues aim to further analyze T. rex fossils to search for bite marks inflicted by their own kind.
“Evidence of bite marks on skulls and other bone parts is well-documented in T. rex and other carnivorous dinosaurs. If T. rex shows fewer bite marks on its forelimbs compared to its ancestors, that could indicate that the reduction in size was effective,” Padian added.
The forelimbs of Tyrannosaurus rex, although very small, are also a crucial part.
Additionally, the forelimbs of Tyrannosaurus rex may have been used to support the body and maintain stability, helping them balance and manage a variety of complex movements, such as turning and jumping.
Therefore, while the tiny forelimbs of Tyrannosaurus rex may appear insignificant, they are actually a very important part that helps maintain stability, cope with various complex movements, and plays a crucial role in chasing prey.
Overall, Tyrannosaurus rex was a very powerful, fierce, and intelligent dinosaur, one of the most fearsome predators of its time. Although it was not the only apex predator, its body structure, intelligence, and aggressive habits made it the ruler of the ecosystem during that era.
