By - - BBC NEWS
Added: Fri, 16 Sep 2011 02:57:21 UTC

Samples of amber in western Canada containing feathers from dinosaurs and birds have yielded the most complete story of feather evolution ever seen.

Eleven fragments show the progression from hair-like "filaments" to doubly-branched feathers of modern birds.

The analysis of the 80-million-year-old amber deposits is presented in Science.

The find, along with an accompanying article analysing feather pigment, adds to the idea that many dinosaurs sported feathers - some brightly coloured.

Recent years have seen a proliferation of reports about the beginnings of feathers as we know them now in birds.

So-called compression fossils found in China bear outlines of primitive "filament" feathers that are more akin to hair.

But modern feathers are highly branched and structured, and the full story of how those came to be had not yet been revealed by the fossil record.

Now a study of amber found near Grassy Lake in Alberta - dated from what is known as the Late Cretaceous period - has unearthed a full range of feather structures that demonstrate the progression.

"We're finding two ends of the evolutionary development that had been proposed for feathers trapped in the same amber deposit," said Ryan McKellar of the University of Alberta, lead author of the report.

The team's find confirms that the filaments progressed to tufts of filaments from a single origin, called barbs. In later development, some of these barbs can coalesce into a central branch called a rachis. As the structure develops further, further branches of filments form from the rachis.

"We've got feathers that look to be little filamentous hair-like feathers, we've got the same filaments bound together in clumps, and then we've got a series that are for all intents and purposes identical to modern feathers," Mr McKellar told BBC News.

"We're catching some that look to be dinosaur feathers and another set that are pretty much dead ringers for modern birds."

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TAGGED: BIOLOGY, EVOLUTION