T. rex’s short arms may have reduced biting during feeding

T. rex's short arms may have reduced biting during feeding

A large photograph of T. rex in the atrium of UC Berkeley’s Valley Life Sciences Building shows the short form of the dinosaur’s arms, although it was the most ridiculous of its days. Yes: Peg Skorpinski

Over the course of two years, paleontologist Kevin Padian taught a new seminar called The Age of Dinosaurs, one question often asked of him by low -income students: Why are the hands of ʻO Tyrannosaurus rex too short?

He often adhered to the various hypotheses proposed by paleontologists – for marriage, for capturing or re -capturing a captive, for reaping on the spot. Triceratops—But his students, always looking at the meaning of life in his eyes, were skeptical. Padian’s usual response was, “Nobody knows.” But he also believed that the scholars who wanted to solve the conundrum had come from a misconception.

Before asking what By T. rex Short hands were developed to work, says Padian, the question is what those hands need for the whole animal.

On a paper that appears in the issue of a journal Acta Palaeontologia PolonicaPadian hopes for a new hypothesis: The By T. rex the arms are less long to prevent being cut or felt during a group T. rexes down on the corpse with their large heads and skeletal teeth. It is 45 feet long T. rexfor example, a skull is 5 feet long, but the arms are 3 feet long – it looks like a 6 -foot man with five hands.

“What if some adult tyrannosaurs meet on the corpse? You have a large group of heads, with very strong necks and teeth, that tear and cut the flesh and bone near you. Very close to you. ? They can teach you by cutting your arm, “said Padian, honorary physician emeritus of integrative biology at the University of California, Berkeley, and a curator at the UC Museum of Paleontology (UCMP). ). “So it’s probably an advantage to reduce the first limbs, even if you don’t use them for predation.”

Severe back pain can cause pain, hemorrhaging, tremors and postpartum death, he said.

Padian found that the first tyrannosaurids had longer arms, so there was a reason the group decreased in size and mobility. This is just not the case T. rexwho lived in North America at the end of the Cretaceous period, he said, but the African and South American abelisaurids from the middle of the Cretaceous and the carcharodontosaurids, which were intertwined in Europe and Asia in the Early and Mid-Cretaceous period. more T. rex.

“All the ideas that have been left about this have not been tested or are impossible because it is impossible to do,” Padian said. “None of the hypotheses explain why the hands are so small – the best thing they can do is explain why they keep the hands so small. It’s reduced.”

He admitted that a hypothesis would be difficult, according to his, to prove 66 million years later. T. rex completely lost.

Hands and arms T. rex

When the great dinosaur hunter Barnum Brown first saw it T. rex In 1900 he believed that hands were too small to be pieces of bone. His colleague, Henry Fairfield Osborn, explained and named T. rex, referred to as “pectoral claspers” are short arms – the limbs that hold a woman in during confinement. This compares with some pelvic and pelvic floor claspers, which have been modified. But Osborn gave no evidence, and Padian knew By T. rex the arms are too short to go around the other T. rex and is too weak to exercise power over a partner.

More than a hundred other explanations are intended for short hands that include pulling a friend or a social signal, becoming an anchor of acceptance. T. rex arise from the earth, take the captive, stab the enemy, and drive away sleep Triceratops at night. Consider cattle rustling, says Padian. And some paleontologists think that the hands don’t work, so we don’t have to worry about them.

Padian approached the question in a different way, questioning the usefulness of short arms for the survival of the animal. The answer came after other paleontologists saw evidence that some tyrannosaurids were found in the bags, not one, as shown in the paintings and in dioramas.

“Some of the most important quarry sites that have been seen in the last 20 years also care for both adult and juvenile tyrannosaurs,” he said. “We can’t really believe they lived together or died together. We just know they were buried together. But when you see some cells with the same animals, the signal is stronger. That they fed. That is what they are going after. “

She probably thought her hands were too small to go out of the way while she was feeding. T. rex Young people, that is, it is wise to wait until all the adults are older.

In his latest paper, Padian looks at the hypotheses of other paleontologists, none of which have been found to have been fully tested. The first thing he decided to do was to measure the amount of life T. rex the thrower to control the atrium outside the UCMP gates, none of the hypotheses actually work.

“The arms are very short,” he said. “They can’t touch each other, they can’t reach their mouths, and their movement is so restricted that they can’t reach very far, forward or upward. It’s like a machine. death you saw in ‘Jurassic Park.’ “

Twenty years ago, two paleontologists analyzed the hands and found that T. rex it can hold about 400 pounds with its hands. “But the thing is, it’s impossible to get close to anything to get,” Padian said.

Beware of Komodo dogs

Padian’s hypothesis is a comparison to some of the most dangerous animals today. The giant Komodo Dragon (ʻO Varanus komodoensis) Indonesia pursues in groups, and when killing the captive, large dragons congregate on the corpse and leave the remains for the smaller ones. It can be destructive, as it does among crocodiles during feeding. Probably so T. rex and other tyrannosaurids, first seen in the Late Jurassic until their peak in the Late Cretaceous before extinction.

The hypothesis cannot be fixed, Padian said, but a connection could be made if clinical evidence around the world is looked at for symptoms of bites. Fossil crowdsourcing is a very good thing, he agreed.

“Injuries to the head and other parts of the bone are very common in tyrannosaurs and other carnivorous dinosaurs,” he said. “If there are fewer bite marks found in the small branches, it’s probably a sign that the reduction is working.”

But Padian has no idea that his opinion is the end of the story.

“The first thing I wanted to do was to create a non -work of traditional ideas,” he said. “It brings us back to the same number. Then we can take an integrated approach, thinking about community, nutrition and ecological factors without thinking about the mechanical. “

Another problem in establishing the hypothesis is that many groups of large carnivorous dinosaurs independently reduced their primary limbs, albeit in different ways.

“The limb bones of these groups are different in size and size, but they have different types of skeletal bones,” says Padian. “We don’t expect them to be reduced in the same way. This is also true for the small wings of our large, live, flightless birds, such as the ostrich, emu and rhea. own. “

Padian finds a common ground in the history of describing short arms and other forms of T. rex.

“For me, this research on hand -made things is interesting because of the way we tell stories in science and the things that are necessary to explain,” he said. “We tell a lot of stories like this about the possible actions of T. rex because it’s an interesting problem. But are we really looking at the problem? “

Padian’s paper is part of a Festschift honoring mammalian paleontologist Richard Cifelli, longtime head of the Museum of Natural History and President of Biology at the University of Oklahoma at Norman.


The flesh of the bones of Quetzalcoatlus, the largest flying creature on Earth


More information:
Kevin Padian, Why tyrannosaur forelimbs are short: a combination hypothesis, Acta Palaeontologica Polonica (2022). DOI: 10.4202 / app.00921.2021

Presented by the University of California – Berkeley

Directions: T. rex’s short arms may have reduced biting when feeding on predators (2022, April 1) Retrieved April 1, 2022 from https://phys.org/news/ 2022-04-rex-short-arms-lowered-frenzies. html

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