Feathered ancestor of T. rex unearthed
Fossil strengthens case for downy monsters.
Ancestors of the fearsome Tyrannosaurus rex were clothed in delicate feathers, a fossil discovered in China suggests. The find may come as a surprise to people used to images of Tyrannosaurus as a scaly monster. But many palaeontologists have been predicting just such a find ever since the first evidence of a dinosaur with a feathery coat came from the same site in Liaoning in 1995.
The 130 million-year-old fossil is the oldest member recorded from the tyrannosauroid family, and the first in the group with a feather-like covering. The discovery of its skull and other fragments is reported today in Nature1.
The new dinosaur has been christened Dilong paradoxus. Dilong means Emperor dragon. "We added paradoxus to its name because it's so counter-intuitive to think of feathers and a Tyrannosaurus together," says team member Mark Norell at the American Museum of Natural History in New York city.
Evidence of these so-called protofeathers is usually difficult to find because feathers decay when they are exposed to oxygen. But at Liaoning, the specimens appear to have been buried extremely quickly under fine-grained volcanic ash, helping to preserve the soft, feathery outlines.
American Museum of Natural History, New York
"Dilong is an exciting find because it's so complete," says palaeontologist Thomas Holtz of the University of Maryland in College Park, "and the feathers are the icing on the cake."
Holtz hopes that the new evidence will convince the scientific community that feathers evolved on dinosaurs long before the appearance of birds. Until now, some palaeontologists have been dubious that feathered tyrannosauroids existed.
Feathered and petite
The jackal-sized Dilong was far smaller than T. rex, which roamed the Earth some 65 million years later. But Dilong shares many of its characteristics.
The meateater probably had a broad, square skull and powerful jaws, says Holtz. But while the forelimbs of T. rex had dwindled until they were almost useless, Dilong would have been able to clutch food in its hands and bring it to its mouth.
Dilong's protofeathers are not what we would recognise as feathers today, but are their evolutionary precursors. Rather than having a central shaft and barbs, they are single flexible filaments that would have covered the dinosaur's body like hair.
The protofeathers would most likely have been used for insulation rather than flight, Norell says. The giant T. rex had probably lost the featherlike features of its predecessors because, with its much larger size, it would have had more difficulty losing heat than keeping it. Tyrannosaurus chicks may have had a downy cover, though.
However, the discovery of feathered dinosaurs at Liaoning is trickling down into popular culture. The first Jurassic Park film featured mainly scaly reptiles, Norell says, "But from what I've seen of the first shots of Jurassic Park IV, all the dinosaurs now have feathers."
- Xu X., et al. Nature, 431. 680 - 684 (2004).