Could giant feathered dinosaur hint at feathers for T.rex?

11 April 2012

The largest dinosaur ever to be found with feathers was unveiled last week. Yutyrannus huali was in the same group of meat-eating dinosaurs as T.rex. Until now, only small dinosaurs with feathers had been uncovered. But weighing 1.4 tonnes, this animal shows that big beasts could have had feathers too.

Fossil tail feathers of Yutyrannus

Fossil tail feathers of Yutyrannus. The rock where this fossil was uncovered is unusual in that it allows fragile, easily decomposed structures, like feathers, to be fossilised. © Zang Hailong

So, how likely is it that Tyrannosaurus rex had feathers? Natural History Museum dinosaur expert Dr Paul Barrett gives his view. 'This new find suggests that even large meat-eating dinosaurs might have had feathers, so it does hint at the intriguing possibility that an adult T.rex, though it was much larger than Yutyrannus, might also have had feathers'.

However, Barrett suggests it may have been the young rather than adults that had feathers. 'I think it’s quite likely that hatchling and young T.rex might have had a downy covering and possibly some feathers'.

Beautiful feathered tyrant

Yutyrannus huali, means 'beautiful feathered tyrant'. The 1.4 tonne animal lived around 125 million years ago during the Early Cretaceous Period. It belonged in the tyrannosauroid group that included dinosaurs with characteristic short arms and powerful jaws, like T.rex.

The Yutyrannus fossils were unearthed from the Yixian Formation in northeastern China, and the new species was identified by a team led by Xu Xing from the Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences.

There are 3 near-complete fossils and they show long filamentous feathers. Barrett was lucky enough to see them for himself when he visited the institute recently as part of his research. 'The bones are on large slabs of rock and are generally still preserved attached together, with clear feathers preserved around the bones.'

'This is the second member of the tyrannosaur family to be shown to possess feathers,' adds Barrett. 'It is also the largest ever animal known to possess a covering of feathers, at least for now.'

Looking for T.rex feather evidence

Could scientists have missed minute signs of feathers in existing T.rex fossils? Barrett thinks not. 'Existing specimens of T.rex show no evidence of feathers at all. We’d need to find new specimens that were preserved in exactly the right way to prove that this massive carnivore had plumage.'

It's all in the rocks
Fossil skull of Yutyrannus. One of 3 well-preserved fossils uncovered in northeastern China.

Fossil skull of Yutyrannus. One of 3 well-preserved fossils uncovered in northeastern China. © Zang Hailong

The type of rock the animal is preserved in is crucial. Evidence of feathers and other easily decomposed soft tissues aren’t preserved in the rock types that T.rex fossils have been found in.

'We only know that Yutyrannus was feathered because its remains are preserved in unusual rocks whose composition and chemistry allow the fossilisation of these fragile, easily decomposed structures,' says Barrett.

What use were dinosaur feathers?

Dinosaur feathers would have had several functions. Barrett explains, 'They would have helped to keep dinosaurs warm, which would be particularly important for small, active dinosaurs.

'They could also have been used to incubate eggs, by holding the eggs under the feathers to keep them warm.

'In addition, feathers are often brightly coloured and can be large and strikingly shaped: in these cases they are used for display, to attract mates for example.

‘And of course, birds are also dinosaurs and in this case they are also used for flight.'

Downside to feathers?

Finding feathers in such large animals has surprised to scientists. ‘It's generally been thought that very large dinosaurs would lack feathers due to problems with over-heating,' says Barrett, 'as the feathers act as insulation and large dinosaurs would have retained a lot of body heat, simply because of their large size, so feathers would make this problem worse’.

More feathered finds to come?

Finding more feathered dinosaur fossils elsewhere in the world could be key to understanding more about the appearance and behaviour of the whole meat-eating dinosaur (theropod) group.

Barrett concludes, ‘If similar fossil sites were found outside of China, I think that many theropods would be shown to have feathers’.

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