Palaeontologists in China have uncovered a species of giant feathered dinosaur that was an ancient relative of Tyrannosaurus Rex. Scientists have known for over a decade that some small dinosaurs had bird-like feathers. But a report in the journal Nature says the new species of tyrannosaur, which was 9 metres long and weighed about 1.5 tonnes, provides direct evidence of the existence of gigantic feathered dinosaurs and has implications for early feather evolution.
The theropod, which was an ancient relative of Tyrannosaurus Rex, was 40 times larger than any previously known feathered dinosaur. It has been given the name Yutyrannus Huali, a combination of Latin and Mandarin, which means “beautiful feathered tyrant”.
The paper’s lead author, Professor Xu Xing from Beijing’s Institute of Vertebrate Palaeontology and Palaeoanthropology, says the new species is based on three beautifully preserved specimens. ”The feathers of Yutyrannus were simple filaments,” Professor Xu said. ”They were more like the fuzzy down of a modern baby chick than the stiff plumes of an adult bird.”
The almost complete skeletons were found near each other in a quarry in the famous dinosaur fossil beds of Liaoning Province in north-eastern China. They date back to the lower Cretaceous period between 130 and 125 million years ago.
At the time the area was an anoxic lake bed. The lack of oxygen helped preserve the animals that died there, and prevented bugs and scavengers from destroying the remains.
The two smaller specimens are thought to be juveniles and were fully articulated, meaning their skeletons were positioned as they would be if the animals were still alive. They weighed about half a tonne each and were found together, on their sides and with their necks arched backward.
Professor Xu and colleagues believe the large size of Yutyrannus and the downy structure of its feathers would have made flight an impossibility, but they argue that the feathers may have provided the animals with insulation keeping them warm.
Palaeontologist Dr Eric Roberts from James Cook University in Queensland, says it was thought that large dinosaurs did not need feathers to keep warm because their huge body mass to surface area allowed them to retain most of their heat.
“In fact for big dinosaurs, getting rid of excess heat was the problem,” Dr Roberts said. But he points out that while the Cretaceous was generally very warm, Yutyrannus lived at a time when Liaoning Province was much cooler due to its latitude and elevation.
“The fossils are also interesting because they include a combination of primitive features compared to other tyrannosauroids,” Dr Roberts said. ”These include having three rather than two fingers on each hand, having different muscle attachment ridges on the bones and showing growth patterns which appear to be more similar to Allosaurus than T Rex. This is exciting stuff, providing palaeontologists with a greater insight into the evolution of dinosaurs.”
source: afp/nature/ brian choo