Did Dinosaurs Really Have Feathers?
Science is learning more and more about the versatility of form in dinosaurs with each great find in China, the Americas, Antarctica, and elsewhere. During their heyday in the Triassic, Jurassic, and Cretaceous periods, dinosaurs evolved to fill niches in most ecosystems. Some were large, some were small, some walked on land, some were amphibious, and some dinosaurs even possessed the ability to fly. But did they have real honest-to-goodness feathers? Recent research shows that they did, but this isn’t the end of the story.
For many years science has known that the only remaining descendants of the dinosaur lineage are the birds. (So, if anyone asks you whether dinosaurs really died out at the end of the Cretaceous, you can point out the window at our feathered friends.) One of the most surprising developments in paleontology in recent years has been the discovery that, like birds, dinosaurs—many dinosaurs, in fact—possessed feathers. It stands to reason that if birds have them, they must have evolved in something older, right?
Let’s take a quick look at feather design. The typical feather in modern birds consists of a central shaft (rachis), with serial paired branches (barbs) forming a flattened, usually curved surface—the vane. The barbs branch into barbules, and the barbules of adjacent barbs are attached to one another by hooks, stiffening the vane. In many birds some or all of the feathers lack the barbules or hooks, and the plumage has a loose hair-like appearance. The precursors of bird feathers were simple, straight, dense, filamentous structures made mostly of keratin. These eventually evolved into branched, then downy, structures in several stalked forms that soon disappeared. Over time, this branched condition resolved itself into a central stalk with vanes on either side, and these vanes later evolved into barbs.
The first dinosaur fossils with structures that could be considered feathers were found in the 1990s. Other discoveries followed. By 2011 some studies were even suggesting that all dinosaurs had some type of feathery covering on at least some parts of their bodies—in much the same way that all mammals have hair but not all mammals are hairy. Even though the first dinosaurs are thought to have emerged some 245 million years ago, dinosaurs with feathers have been dated to only 180 million years ago. Yet, the story does not end there.
Feathers, it seems, did not originate with the dinosaurs. According to a recent study, they may have evolved in another group. The pterosaurs, a closely related but separate group of “ruling reptiles” (or archosaurs, a group that, incidentally, also includes birds and crocodiles), also had feathers. A study of pterosaur fossils published in 2019 described the presence of branching featherlike structures called pycnofibres in pterosaur fossils dating to about 160 million years ago. These feathers appeared in tufts; they were not simple and straight, which suggests that the origin of feathers predated both the pterosaurs and the dinosaurs and occurred in a common ancestor some 250 million years old or older.