Source: Nature | By Matt Kaplan

Birds evolved from dinosaurs, and dinosaur fossils are often covered with impressions of feathers, which made some palaeontologists speculate whether feathers were a common trait that appeared early in their history. Now a team analyzing feathers on the overall dinosaur family tree argues this is taking things too far.

Palaeontologists have known for about two decades that theropods, the dinosaur group that contained the likes of Tyrannosaurus and Velociraptor and from which modern birds evolved, were covered in feathery structures from early on in their history.

By contrast, the ornithischian lineage — which contained animals such as Triceratops, Stegosaurus and Ankylosaurus — and the huge, long-necked dinosaurs in the sauropod lineage were considered to be scaly, similar to modern reptiles. Indeed, all evidence pointed in this direction until the discovery, beginning in 2002, of a few ornithischians with filament-like structures in their skin. This led to speculation that feather-like structures were an ancestral trait for all dinosaur groups.

Keen to know more, palaeontologists Paul Barrett of the Natural History Museum in London and David Evans of the Royal Ontario Museum in Toronto created a database of all known impressions of dinosaur skin tissues. They then identified those that had feathers or feather-like structures, and considered relationships in the dinosaurian family tree.

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