Ohio University professor Lawrence M. Witmer said Tianyulong's discovery has "made an already confusing picture of feathers' origins even fuzzier".

"Before the 1990s, life was simple," he explained.

Feathers were believed to be an exclusively avian attribute, found in all birds today and extending back some 150 million years ago to the iconic Archaeopteryx of the Late Jurassic Period.

But the picture became muddled after the 1996 discovery of predatory theropods in Liaoning that were covered in avian-like feathers, forcing scientists to acknowledge feathered dinosaurs as modern birds' evolutionary ancestors.

Tianyulong's discovery suggests both the two orders of dinosaurs - Saurischia and Ornithischia - developed proto-feathers.

And because Tianyulong was among the most primitive of early dinosaurs, it stands to reason that "the origin of feathers might go right back to the origin of dinosaurs as a whole, more than 200 million years ago", Witmer said.

You said: "In order to bring the evolutionary picture of feathers into sharper focus, scientists have to look back to the origin of dinosaurs, even beyond dinosaurs."

But other controversies surround the find.

Most scientists presume Tianyulong's dino-fuzz grew outside, rather than inside, its skin. But, Witmer said, although it is unlikely the structures were dermal (inside the skin), it cannot be known for sure they were epidermal (outside the skin).

"The difference between epidermal and dermal is huge," he said.

"If they are epidermal, then they bear not only on feather evolution and avian origins but also on metabolic physiology, behavioral display and flight.

"If they are dermal, then they're ultimately structural in function and have little bearing on those other issues."

You said further research using biochemical and molecular technologies will provide more assertive answers. But from what is known now, the filaments' attributes suggest they were epidermal.

(China Daily March 19, 2009)