Fossils show feathered reptile was big and furry 125 million years ago
The group of theropods that gave rise to modern birds are part of a group known as tyrannoraptors, and include everyone's favorite two-legged predator, Tyrannosaurus rex. Does that mean Tyrannosaurus rex was furry? Scientists have tried to find an answer to this question.
Photo: australian.museum
The idea that birds are dinosaurs was first proposed in the mid-19th century, but it was confirmed by the discovery of the Archaeopteryx fossil in 1861. Since then, evidence of feathered dinosaurs has appeared in several groups around the planet, but the title of largest feathered dinosaur currently belongs to Yutyrannus huali.
«We found Tyrannosaurus rex fossils with patches of skin on them, so we at least know they weren't completely covered in feathers as adults,» — experts say.
Feathered dinosaurs existed, just look at Dilong paradoxus. It was also a ferocious predator, although much smaller in size, but possessing a number of features that mirrored Tyrannosaurus rex, including large jaws and close-fitting front teeth. It also had a thin layer of feathers, which scientists believe helped it retain heat.
Then came Yutyrannus huali, whose name literally means “beautiful feathered tyrant.” It was described in 2012 and is the largest dinosaur discovered to date that paleontologists are confident had feathers.
At around 9 meters long and weighing an estimated 1,400 kilograms, it is four times heavier than the previous title holder, Beipiaosaurus – a relative of the therizinosaur that surpassed Yutyrannus huali.
Whether Yutyrannus huali was partially or fully feathered is still a matter of debate, but it had proto-feathers that were different from modern ones. These were long filaments (about 20 centimeters, according to the Australian Museum) that lacked the barbs, barbs and hooks that modern feathers now have, but are believed to have formed a shaggy wool that allowed Yutyrannus huali to stay warm in cold climates .
The dinosaur lived about 125 million years ago, during the Early Cretaceous period, so it is possible that feathers as a distinctive feature of tyrannosaurs were lost by the time Tyrannosaurus rex appeared. The baby Tyrannosaurus rex is thought to have been the size of a terrier and may have had a coat of fluffy proto-feathers.
One logical reason to doubt that adult Tyrannosaurs were feathered comes down to their physiology. As Tyrannosaurus rex grew, its body volume greatly exceeded its surface area (skin), meaning that from a metabolic point of view it made no sense to be covered in feathers, since it would be too hot.
«The Tyrannosaurus Problem rex was not that he was cold, but quite the opposite, — paleontologists say. — When he was small and had a high surface area to body volume ratio, he would have benefited from the warmth of a feather down jacket. However, this approach was probably not associated with gigantism, and therefore feathers were lost in some groups but retained in others, including the dinosaurs with which we share this planet today.