Did pterosaurs also have feathers – similar to some dinosaur species? This question, which has been the subject of heated debate up to now, now seems to have been resolved: in addition to traces of hair-like filaments, paleontologists have also discovered branched structures in a pterosaur fossil that are similar to those of modern-day bird feathers. They also found evidence that these feathers and the areas of skin surrounding them were colored and thus possibly also served show effects. The study sheds new light on the evolution of feathers and their functions, say the researchers.
In the case of dinosaurs, it is now clear that many species already had complex feathering. Even the fine structure of their feathers was clearly visible in some finds. What distinguished these structures from hair was their complex branching. According to this, some representatives of the dinosaurs only had down-like plumage that kept them warm – but there were also more complex feather shapes that presumably played a role in courtship behavior. At some point, some dinosaurs also developed feathered wings that they could use to fly into the air. They then became the ancestors of today’s birds.
On the trail of pterosaur feathers
So it was obvious that the dinosaurs were the “inventors” of feathers. But this assumption was called into question in 2018: Paleontologists had discovered evidence of branched feather structures in addition to the already known hair-like structures in pterosaurs. The decisive aspect is that pterosaurs were not representatives of the dinosaurs, but only their relatives – the development lines of both groups separated more than 250 million years ago. Thus, feather finds in the flying reptiles are something special. However, the structures discovered so far could also have been misinterpreted, some paleontologists have criticized. However, the scientists led by Aude Cincotta from University College Cork are now presenting new, very clear evidence of pterosaur feathers.
The findings come from the examination of a particularly detailed preserved head of a Tupandactylus imperator from Brazil. These representatives of the pterosaurs had a wingspan of about five meters and were characterized by a particularly distinctive crest on their heads, which probably represented an intraspecific show element. As Cincotta and her colleagues report, the traces of fine structures in the back part of this ridge aroused their special interest. In order to uncover further details, they therefore subjected the area to an electron microscopic examination.
Their discoveries show that the animal had a crown of feathers on the underside of its crest: in addition to hair-like filaments, the researchers also found traces of fluffy, branched structures there, the characteristics of which are similar to those of bird feathers. “Paleontologists have debated for some time whether or not pterosaurs had real feathers. Our specimen’s feathers now put an end to this debate for good, as they are clearly branched along its entire length, just like in modern birds,” says Cincotta.
Colored plumage stands out
During their investigations, the paleontologists also discovered traces of so-called melanosomes in the feathers and in the remains of the animal’s skin. These are structures in which the pigment melanin is located. The detailed investigations also showed that the melanosomes in the filaments, the feathers and the skin had different shapes. “In contemporary birds, plumage color is strongly linked to melanosome shape,” explains co-author Maria McNamara of University College Cork. “Because pterosaur feather types had different melanosome shapes, these animals must have had the genetic machinery to produce different feather colors. This feature is critical to color matching,” says McNamara.
Specifically, the study results suggest that the head of Tupandactylus imperator was not only impressively shaped, but also colored: The colors and patterns created by the feather structures could also have played a role in the intraspecific communication of these pterosaurs. Thus, there are clear parallels to the findings in some dinosaur species. This, in turn, is an important clue about the origin of the evolution of feathers: if pterosaurs also possessed the structures, it stands to reason that the innovation goes back to the common ancestor of pterosaurs and dinosaurs.
According to this, a creature could have produced the first feather-like structures around 250 million years ago – presumably initially to keep warm. However, the role of feathers as elements of visual communication may also have deep evolutionary roots. “The new study results could now lead to a reorientation towards studying the insulating ability of feathers, which was probably the main reason for their development – followed by their use as signaling structures,” writes Michael Benton of the University of Bristol in a comment on the study .
Source: University College Cork, Article: Nature, doi: 10.1038/s41586-022-04622-3