Feathered, Bird-Like Dinosaur Anchiornis Was Even Fluffier than We Thought

A study published this week in the journal Palaeontology has revealed new details about feathers of the chicken-sized, feathered, bird-like dinosaur Anchiornis.

A new depiction of Anchiornis and its contour feather. Image credit: Rebecca Gelernter.

A new depiction of Anchiornis and its contour feather. Image credit: Rebecca Gelernter.

Anchiornis lived in what is now northeastern China during the Jurassic period, about 160 million years ago.

This dinosaur had wing-bearing arms, long legs, and a long tail. It had a wing span of up to 1.64 feet (0.5 m), grew to about 1.3 feet (0.4 m) long, and weighed 0.1-0.25 kg.

In the new study, University of Bristol paleontologists Dr. Evan Saitta and Dr. Jakob Vinther examined an exceptionally-preserved fossil of Anchiornis.

The researchers then compared the species’ fossilized feathers to those of other dinosaurs and extinct birds.

Anchiornis’ contour feathers revealed a newly-described, extinct, primitive feather form consisting of a short quill with long, independent, flexible barbs erupting from the quill at low angles to form two vanes and a forked feather shape.

Such feathers would have given Anchiornis a fluffy appearance relative to the streamlined bodies of modern flying birds, whose feathers have tightly-zipped vanes forming continuous surfaces.

Anchiornis’ unzipped feathers might have affected the dinosaur’s ability to control its temperature and repel water, possibly being less effective than the vanes of most modern feathers. This shaggy plumage would also have increased drag when Anchiornis glided.

Additionally, the feathers on the wing of Anchiornis lack the aerodynamic, asymmetrical vanes of modern flight feathers, and the study shows that these vanes were also not tightly-zipped compared to modern flight feathers. This would have hindered the feather’s ability to form a lift surface.

To compensate, paravian dinosaurs like Anchiornis packed multiple rows of long feathers into the wing, unlike modern birds, where most of the wing surface is formed by just one row of feathers.

Furthermore, Anchiornis and other paravians had four wings, with long feathers on the legs in addition to the arms, as well as elongated feathers forming a fringe around the tail. This increase in surface-area likely allowed for gliding before the evolution of powered flight.

To assist in reconstructing the updated look of Anchiornis, scientific illustrator Rebecca Gelernter worked with the team to draw the animal as it was in life.

The new piece represents a radical shift in dinosaur depictions and incorporates previous research.

“The novel aspects of the wing and contour feathers, as well as fully-feathered hands and feet, are added to the depiction,” Dr. Saitta said.

“Most provocatively, Anchiornis is presented in this artwork climbing in the manner of hoatzin chicks, the only living bird whose juveniles retain a relic of their dinosaurian past, a functional claw.”

“This contrasts much previous art that places paravians perched on top of branches like modern birds.”

“However, such perching is unlikely given the lack of a reversed toe as in modern perching birds and climbing is consistent with the well-developed arms and claws in paravians.”

“Overall, our study provides some new insight into the appearance of dinosaurs, their behavior and physiology, and the evolution of feathers, birds, and powered flight.”

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Evan T. Saitta et al. Additional information on the primitive contour and wing feathering of paravian dinosaurs. Palaeontology, published online November 28, 2017; doi: 10.1111/pala.12342

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