Feathered Dinosaurs Suffered More Drag, But Were Gorgeously Fluffy

How feathers have changed over 160 million years. University of Bristol

It doesn't quite fit with the popular images of ferocious killing machines, but in recent years palaeontologists have been discovering that many dinosaurs had feathers, although there is debate as to just how common this was. Investigation into one species, however, reveals the feathers were rather different from those seen on modern dinosaurs – i.e. birds. The ancient version appears to have been considerably less efficient than today's equivalent, but would have made its owners considerably cuter.

Anchiornis was a small carnivorous dinosaur that lived around 160 million years ago. An exceptional specimen has allowed University of Bristol researchers in the UK to examine its feathers in a detail never previously achieved for a Jurassic species. Some of the feathers fell off the body prior to fossilization, allowing us to see them with unprecedented clarity.

PhD student Evan Saitta reports in Palaeontology that Anchiornis' feathers were made up of a short quill from which independent barbs extended at low angles, creating a V shape with a large gap between the arms. These appear to have been much less aerodynamic than the continuous surfaces of modern feathers, causing extra drag that would have interfered when Anchiornis attempted to glide, yet to invent true flight.

Anchiornis' feathers were also probably inferior to those of today's birds in terms of both temperature control and water resistance.

Natural selection has a way of making the best of bad tools, however, and Anchiornis partially compensated by having multiple rows of feathers on its wings, rather than a single row like modern birds. As we already knew, extra lift was provided by having four wings, with the legs carrying long feathers that could assist in gliding, and extended feathers on the tail.

If the feathers were not that great for practical uses, they were at least aesthetic, with the body feathers giving adult Anchiornis a fluffy look, like a duckling.

“Our study provides some new insight into the appearance of dinosaurs, their behavior and physiology, and the evolution of feathers, birds, and powered flight,” Saitta said in a statement.

Since Anchiornis could only glide, rather than fly, it must have climbed trees to gain altitude. Others have envisaged it perching on branches like birds do today, but Saitta considers this unlikely without the reversed toe of perching birds like owls and most parrots. Instead, he argues Anchiornis' strong arms and claws would have enabled it to climb like hoatzin chicks, the only living bird that has claws like ancient dinosaurs, albeit only in juveniles.

Artist's impression of the Jurrasic dinosaur Anchiornis, which was about the size of a crow. Note not only the feathers, but the way it is climbing the branch. Rebecca Gelernter

 

 

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