The mystery of T. rex's Little Arm has been answered, its head is the main weapon

JAKARTA - The arms of Tyrannosaurus rex have often been the subject of jokes. Its body is gigantic, its jaws are terrifying, but its arms are so short. A new study says T. rex no longer relies on its arms to hunt. The role is taken over by its much stronger head and jaw.

According to a report by The Independent, which was quoted on Thursday, May 22, a study published in the journal Proceedings of the Royal Society B Biological Sciences said that the small arms of T. rex were related to the development of a large and strong skull.

T. rex could grow about 40 feet or 12 meters long, and 20 feet or 6 meters tall. However, its front legs were only about 3 feet or less than 1 meter, not far from the length of a human arm.

According to researchers, this body change occurs when the size of the dinosaur prey also gets bigger. One of them is sauropods, long-necked herbivorous dinosaurs that can reach 100 feet or about 30 meters.

"We are trying to understand what drives this change and find a strong relationship between the short arms and the big head that is formed very strongly," said Charlie Roger Scherer, author of the study from University College London.

"The head takes over the role of the arm as a method of attack. This is a case of 'use it or lose it'. The arm is no longer useful and its size shrinks over time," he said, quoted by The Independent.

In the prehistoric world, grabbing a giant sauropod with claws is not the most effective option. A strong jaw is more useful for attacking and holding prey.

The researchers say the increasing size of prey likely triggered an "evolutionary arms race". This means that predators and prey both change to survive. In this case, the predatory dinosaurs developed stronger skulls and jaws.

In the study, scientists measured the sturdiness of the skull from head size, head bone attachment, and bite strength. T. rex scored the highest, followed by Tyrannotitan, a bipedal dinosaur that was almost as big as T. rex and lived in modern Argentina during the Early Cretaceous period, about 145 million to 100 million years ago.

Researchers also compared arm lengths and skull sizes in five groups of dinosaurs. The results showed that shrinking arms were more strongly linked to sturdy skulls than skull size alone or overall body size.

They also noted that some smaller-bodied predatory dinosaurs still had powerful heads and short front legs.

The researchers concluded that the front legs of the large theropod dinosaur shrank because they were no longer important in catching prey. Theropods are a group of meat-eating dinosaurs that walk on two legs, including T. rex.

In a follow-up study, the researchers wanted to understand how the function of the small forelimbs contributed to the evolution of feathers and flight ability.

"These events resulted in a shift from incapacitating prey with front legs gripping to using powerful bites and sturdy skulls," the researchers wrote.