Pterosaurs Were Strutting Their Stuff in the Early Cretaceous

A gaudy bunch, birds. Lizards are no slouches either when it comes to coloration. Maybe, therefore, their relatives the dinosaurs and pterosaurs blazed with color too. The science of detecting color signals in a long-dead animal is a work in progress. But meanwhile, the discovery that many – possibly all – dinosaurs were feathered at least at some stage in their life cycle spurred imaginations to run riot.

Dinosaurs and pterosaurs are now often depicted as having extravagantly colored and shaped crests, frills, spikes, spines, stripes, blotches and, of course, feathers. At this point, though, it is still not entirely clear who had feathers, let alone what colors they were.

But now a new paper published in Nature casts light on the potential colors on the head of a pterosaur that last soared the skies of Brazil 113 million years ago.

The study also helps puts to bed a controversy: whether or not pterosaurs had “true” feathers as opposed to fuzz. Yes, there is an argument that the aviating animals didn’t have feathers while other ground-bound dinosaurs did. Such was life. There is even speculation that baby pterosaurs could fly pretty much as soon as they hatched, if not particularly well. They would have flown like mama: with stretched skin.

There is other speculation, at the other end of the paleorainbow, that the biggest pterosaurs, the azhdarchids, with wingspans of up to 12 meters (nearly 40 feet), couldn’t fly at all. Apparently they certainly could, suggests yet more research that detected cross-strut structures inside the vertebrae of their insanely long necks.

Bottom line: Yes, pterosaurs had feathers, say Aude Cincotta of the Royal Belgian Institute of Natural Sciences, Maria McNamara of the University College Cork, and colleagues.

On the well-preserved partial cranium of a Tupandactylus imperator that lived in Brazil and passed away during the Early Cretaceous, the team detected two types of feathers: simple unbranched monofilaments, and branched feathers with no evidence for secondary branching, explains McNamara. Yes, pterosaurs had feathers, but the paleontologists found no evidence of true flight feathers on their specimen. Nobody to date has found true flight feathers on pterosaurs, the team confirms.

• New Study Suggests Baby Pterosaurs Could Fly
• Did Dinosaurs Have Fleas?
• The Brouhaha Over the 'Bald Pterosaur'

“The specimen that we studied is only a partial cranium. We don’t have the rest of the specimen so we can’t really comment on the appearance of those body parts,” McNamara says. But, she qualifies: “We think it’s extremely unlikely that this pterosaur had true flight feathers, as in stage-five feathers with an asymmetric closed vane. Not only is there no evidence for such derived feathers in the feathered pterosaurs studied to date,” she says, but science is uncertain whether stage-five feathers could have functioned in flight on a pterosaur wing. (Stage five are fully-developed, asymmetric flight feathers.)

If not for flight, what might have been these primitive feathers’ purpose? For one thing, probably thermoregulation. McNamara cautiously points out that with only a partial skull in hand, however well preserved, they can’t confirm that in the case of imperator. In the other two feathered pterosaurs studied to date, the feathers were distributed all over the body, so they clearly played functions in insulation, she says.

Come hither

Being warm in the cold is nice. Procreating is more fun, and another potential function of early feathering in the pterosaur is visual communication – i.e., coloring, to awe the competition, attract mates and so on.

Can it be proven? Not yet anyway, but the researchers did detect melanosomes, in a variety of forms. In fact, they identified a variety of melanosome types in both the imperator’s feathers and skin for the first time in a pterosaur. Until now, this had only been known in theropod dinosaurs and birds.

Melanosomes are primeval microscopic organelles that exist in everything from bacteria to you. They produce and store melanin and other pigments. Melanosomes are responsible for the colors of your hair, your skin, your eyes, your dog and your chicken. (Melanin exists in plants too – note brown and black seeds – but we shall ignore that for the purposes of this article.)

These microscopic organelles may be as ancient as the primordial soup, it has been suggested – meaning they may have evolved billions of years ago. Pigments would have been crucial to early life, as they are to this day: they protect against ultraviolet radiation that damages our DNA; and the melanosomes can enhance the material strength of tissues as in the case of the squid’s beak, and feathers.

In feathers, the melanosomes conferring various colors – hues of brown, gray, reddish brown, orange and black, as well as iridescence – have different shapes.

“The bright colors that you see in some feathers, such as the feathers on the neck of pigeons, the feathers on the chest and back of starlings and magpies – these beautiful shimmering greens and blues and pinks are caused by iridescence. This is an optical phenomenon produced by the layering of very closely packed melanosomes (that can be hollow or solid),” McNamara elaborates.

But it’s complicated. Some colors in feathers are associated with distinct melanosome shapes, such as spheroidal melanosomes and orange/rufous colors, she says. Other melanosome shapes are associated with a range of feather colors.

So elucidating the colors of a fossil animal isn’t as simple as peering through a microscope, getting incredibly lucky and spotting melanosomes with specific shapes.

To be clear, the team did not perform an analysis of the colors on the head of the pterosaur that died in Brazil 113 million years ago. We don’t know what colors imperator had on its head, we do not know its hues or patterning, she spells out.

Ergo, the team cannot confirm that imperator’s feathers served for visual communication – but what are the odds? Since the melanosomes in the different feather types had different geometries, it is likely they had different colors, McNamara says.

So what do we have? A pterosaur that had two different types of feathers on its head and may have had a range of colors, patterning on its head. We don’t know about its body.

And if it did? They could have served the pterosaur for camouflage; and/or they could have served for display. Heaven knows their feathered cousins the birds are into display, some remarkably so, like the birds of paradise.

And now for a moment on evolution. No, birds didn’t arise from pterosaurs, or vice versa, but the existence of branching feathers on the pterosaur indicates that the common ancestor of birds and pterosaurs had them.

Regarding melanosomes specifically in feathers, the study attests that genetic regulation of melanosomes began early in feather evolution. That the genetic mechanisms underlying coloration as an agent of visual communication were already in place in avemetatarsalians, meaning early reptiles, a quarter-billion years ago. And maybe, just maybe, these early feathered friends would strut their stuff for the ladies.