For over a century, the debate about how what dinosaurs truly looked like has raged. In that time, and owing to a poverty of hard evidence beyond fossilized bones, paleontologists have produced some rather wild theories. Whereas some have stuck to the notion that dinosaurs were scaly, others have suggested everything from flat-skin to fur to feathers. And now, it seems that a clear picture may have emerged.

After surveying all the world’s known fossils of dinosaur skin, a pair of paleontologists says the vast majority of non-avian dinosaurs were scaly-skinned, much like reptiles. While the case for certain species of theropods – that gave rise to modern avians – having feathers remains strong, it now seems that these were the exception and not the rule, as some previously thought.

Up until now, opinion remained divided because of the feather-like skin impressions that were found around the fossilized remains of certain theropods, the dinosaur group that contained the likes of Tyrannosaurus and Velociraptor. By contrast, the ornithischian lineage — i.e. Triceratops, Stegosaurus, Ankylosaurus, etc. — and the huge, long-necked sauropod’s were considered to be scaly.

However, 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.

After compiling the data, they then proceeded to identify those that had feathers or feather-like structures, and considered relationships in the dinosaurian family tree. The results, which were revealed back in October at the annual meeting of the Society of Vertebrate Palaeontology, indicate that although some ornithischians had quills or filaments in their skin, the overwhelming majority had scales.

In addition, the survey results suggest that dinosaur feathers, bristles, or fuzz did not arise early enough in the family tree to spread to many non-avian dinosaurs. According to Richard Butler, a paleontologist from the University of Birmingham in the U.K who was not associated with the study, the results are a “valuable reality check” about the appearance of early dinosaurs.

Even so, during an interview with Nature News, Butler was quick to points out that the findings are not set in stone:

We don’t have primitive dinosaurs from the late Triassic and early Jurassic periods preserved in the right conditions for us to find skin or feather impressions. This picture could quickly change if we start finding early dinosaurs with feathers on them.

As a result, paleontologist cannot be precisely sure when or how dino-feathers evolved. If they arose further back in the dinosaur family tree, then more dinosaurs are likely have them. And with new discoveries being made all the time, things may once again tip back in favor of the majority of dinosaurs being feathered, furry or fuzzy.

Source: nature.com, popsci.com