Casuarius, the featherless bird

New skin impressions show the skin of the strange Anthropocene bird Casuarius was a mix of featherless and scaly.

A recently published study looked at all the known skin impressions from the fossils of Casuarius and its close relatives Dromaeus and Struthio to figure out if they had feathers. Previously it was known that Casuarius had featherless wattles on its neck and strange quills thought to be primitive or modified primary feathers on its arms, but there was wide debate on whether the rest of the bird was feathered. Two new skin impressions showing featherless wrinkled skin on the neck and scales on the foot, together from similar patches of featherless and scaly skin on Struthio and a mummified Dromaius lower leg showing scales and scutes, have given researchers the confidence to state that Casuarius together with its relatives were most probably featherless.

The loss of feathers seems to have coincided with evolving giant (for a terrestrial bird) size and be an adaptation for the sweltering heat of the Anthropocene tropics. For such a large animal with a high metabolism the feathers could have been more of a liability, trapping too much of the heat produced by the body of the large avian. To protect the skin on the legs and possibly the whole underside of the animal Casuarius developed hardy scales and scutes. The team adds that it's still possible that some feathers were retained on its back, probably as ornamental vestiges like the quills on the arm. In any case most of the animal's skin was completely naked and possibly brightly coloured.

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This is of course a tongue-in-cheek response to all the news articles prematurely declaring Tyrannosaurus rex fully scaly based on the Bell et al. (2017) paper on tyrannosaur integument. I'm not saying it's impossible that tyrannosaurids were predominantly scaly, but it's worth remembering the lesson of the humble Juravenator.