Artistic representations of pterosaurs, who dominated the skies while dinosaurs ruled the Earth, tend to present them as scaly creatures. These were reptiles after all. However, one family has now been shown to have had both fur and feather-like structures on different body parts. Moreover, the feathers had differing structures depending on where they grew. The discovery was made from two superbly preserved specimens, so we don't yet know how representative they are of the pterosaur order as a whole.
Advances in techniques for imaging fossils have revealed that many extinct dinosaurs not too distantly related to modern birds were also feathered, leading to debate about whether even T-Rexes were part of the feather club. Pterosaurs, including the famous pterodactyls, are sometimes referred to as “flying dinosaurs”, but in fact diverged from dinosaurs (birds included) long beforehand.
Consequently, the discovery of three different kinds of branched feather-like structures on the head and wings of two anurognathids was quite unexpected. The same individuals had a fur-like fuzz on the torso, tails, and limbs, extended onto unfeathered parts of the head.
Fine hairs are of course not unique to mammals, having evolved in nightmare form on many spiders, for example, so their appearance on an extinct reptile isn't a complete shock. The feathers, however, are far more unexpected. They raise the question of whether the first vertebrates to achieve true flight evolved this trait independently, or if feathers date back to a common ancestor of pterosaurs and birds some 250 million years ago. In the latter case, the first dinosaur probably had feathers, suggesting they may have been far more widespread than we previously realized.
The two feathered specimens date to the Mid or Late Jurassic 160-165 million years ago and were found in Yanliao, northern China. The discovery is reported in Nature Ecology and Evolution.
Some of the proto-feather types look more like algae than what one might find on a bird, but others have a clearer stem with thinner branching fibers.
Anurognathids were small pterosaurs with short tails thought to have filled a niche similar to that of insect-eating bats.
Modern birds put feathers to diverse uses, which, the paper notes, “include insulation, tactile sensing, streamlining and coloration (primarily for camouflage and signaling).” Pterosaurs could have used their versions for any or all of these. The authors, led by Nanjing University PhD student Zixiao Yang, argue that for one of the feather types; “The morphology of the structures is consistent with a thermoregulatory function: down feathers can achieve similar insulation to mammalian hair with only about half the mass.” The purposes of some of the other sorts of feathers are harder to determine, particularly the intriguing question of what role they played in flight.