A fossil thought to show feathers on a dinosaur in fact shows the remains of connective tissue, say scientists who have rebutted previous research that suggested an earlier link between dinosaurs and birds had been found.

The fossil studied represented the dinosaur Sinosauropteryx, which lived in the early Cretaceous period roughly 140 million years ago. According to studies conducted in 1998 and 2002, Sinosauropteryx had "protofeathers," which did not allow for flight, but might have provided insulation.

The fossilized remains of the dinosaur Sinosauropteryx does not show signs of feathers, says a new report.
(Zhonghe Zhou, Beijing Museum, Chinese Academy of Sciences)

The discovery was hailed as the earliest example of a dinosaur with feathers, one that would be an important link in evolution to connect dinosaurs to modern birds.

But Theagarten Lingham-Soliar from the University of KwaZulu-Natal in South Africa and his colleagues have published a rebuttal of those findings, arguing the structures thought to be feathers are the degraded remains of collagen fibres, the main connective tissue in animals.

The scientists produced high-resolution microscopic images to show the structures, once thought to be remnants of an early form of feather, were degraded soft tissue from a frill of skin along its neck, back and tail.

They also found no evidence of herringbone-shaped patterns normally seen in feathers.

The study, published in the Proceedings of the Royal Society B on Wednesday, still leaves open the theory that modern birds descended from dinosaurs, but suggests the development of feathers may have occurred in a later period than first thought.

"The pervasiveness of the beguiling, yet poorly supported, proposal of protofeathers in Sinosauropteryx has been counterproductive to the important question of the origin of birds," the authors wrote.