The T. rex is probably the most famous dinosaur of them all, but for years a key question has remained about its anatomy: why were its arms so short?
Now an American paleontologist has claimed the fearsome creature developed stubby arms to keep them out of the way during binge eating.
Having short arms may have reduced the risk of being bitten by other hungry T. rex adults as they devoured a carcass.
The tiny arms of the mighty Tyrannosaurus rex have represented one of paleontology’s greatest and most enduring mysteries.
A 45-foot-long T. rex, for example, might have had a five-foot-long skull, but only three-foot-long arms — the equivalent of a 6-foot human with five-inch arms. .
According to the Natural History Museum, the Tyrannosaurus rex (pictured here) is one of the most fearsome animals to ever exist – but why did it have such light weapons?
The predecessors of tyrannosaurids had longer arms, so there must be a reason why they were reduced in size and joint mobility. This is an artist’s impression of a tyrannosaur eating its prey – a dead hadrosaur
WHAT IS THE T-REX?
Tyrannosaurs rex was a species of bird-like carnivorous dinosaur.
It lived 68 to 66 million years ago in what is now the western part of North America.
They could grow up to 40 feet (12 meters) long and 12 feet (4 meters) high.
Over 50 fossilized T.Rex specimens have been collected to date.
The monstrous animal had one of the strongest bites in the animal kingdom.
Artist’s impression of the T.Rex
T. rex and other tyrannosaurids first appeared in the Late Jurassic and reached their peak in the Late Cretaceous before becoming extinct about 65.5 million years ago.
The new study was led by paleontologist Kevin Padiana, a professor at the University of California, Berkeley and curator at the UC Museum of Paleontology (UCMP).
Professor Padian noted that the predecessors of tyrannosaurids had longer arms, so there must be a reason why they were reduced in both size and joint mobility.
The answer came to him after other paleontologists discovered evidence that some tyrannosaurids hunted in packs, not alone, as numerous paintings and dioramas show.
“What if multiple adult tyrannosaurs converge on a carcass?” he said. “You have a bunch of massive skulls, with incredibly powerful jaws and teeth, tearing and chewing through flesh and bone right next to you.
“What if your friend over there thinks you’re getting a little too close?” They might warn you by cutting off your arm,” he said.
“So it might be beneficial to cut down the forelimbs, since you’re not using them for predation anyway.”
When teaching a freshman seminar called The Age of Dinosaurs, undergrads would always ask Professor Padiana why T. rex arms were so ridiculously short, but the answer was always “Nobody knows. “.
When the great dinosaur hunter Barnum Brown discovered the first T. rex fossils in 1900, he thought the arms were too small to be part of the skeleton.
A life-size cast of T. rex in the atrium of UC Berkeley’s Valley Life Sciences Building shows how the dinosaur’s forearms were particularly short, considering the creature was the fiercest predator of its time. .
At the time, his colleague, Henry Fairfield Osborn, who described and named the T. rex, speculated that the short arms could have been “pectoral clasps” – limbs that hold the female in place during the copulation.
This is analogous to the pelvic claws of some sharks and rays, which are modified fins.
But Osborn offered no evidence, and Professor Padian noted that the T. rex’s arms are too short to reach around another T. rex, and certainly too weak to exert control over a companion.
For more than a century, other explanations offered for the short arms included waving for mate attraction or social signaling, serving as an anchor to allow the T. rex to rise from the ground, clutching prey , stabbing enemies and even pushing on a sleeping Triceratops at night, like a rocking cow.
Also, some paleontologists have proposed that the arms have no function, so we shouldn’t worry about that.
In his paper, Professor Padiana puts forward his new hypothesis – T. rex arms shrunk to prevent accidental or intentional amputation when a group of T. rex descended on a carcass with their massive heads and crushing teeth.
Perhaps the arms have shrunk over the few million years of the species’ existence, only to spread apart during pack feeding.
Young T. rex, in particular, would have been wise to wait until larger adults had finished eating.
This is similar to the largest extant lizard species, the giant Komodo dragon lizard (Varanus komodoensis) from Indonesia.
This extant species hunts in groups and when it kills prey, the larger dragons converge on the carcass and leave the remains for the smaller ones.
Professor Padiana admitted that any hypothesis, including his own, will be difficult to justify 66 million years after the extinction of the last T. rex.
The giant Komodo dragon lizard (Varanus komodoensis, pictured) hunts in groups, and when it kills prey, the larger dragons converge on the carcass and leave the remains for the smaller ones.
“Several significant quarry sites discovered over the past 20 years preserve both adult and juvenile tyrannosaurs together,” he said.
“We can’t really assume they lived together or even died together. We only know they were buried together.
“But when you find multiple sites with the same animals, it’s a stronger signal.” And the possibility, which other researchers have already mentioned, is that they hunted in groups.
Further research could reanalyze T. rex arm fossils for bite marks.
‘Bit bites on the skull and other parts of the skeleton are well known in tyrannosaurs and other carnivorous dinosaurs,’ Prof Padiana said.
“If fewer bite marks were found on the reduced limbs, that could be a sign that the reduction worked.”
The study was published in the journal Acta Palaeontologia Polonica.
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