ScienceSunday: Dino Feathers
Last week, a news story broke with the headline: “All Dinosaurs May have had Feathers“. Gone is the world of scaly lizard-like creatures, roaming through the Mesozoic. Instead, giant fuzz-balls munched on ferns and bird-like creatures hunted the unsuspecting plant-eaters, filling the landscape with bits of color. What caused this sudden paradigm shift, you may ask? A single fossil find: a juvenile of a new species, named Sciurumimus albersdoerferi.
Once again, the news headlines got a bit carried away here. Few paleontologists actually think that Sciurumimus proves all dinosaurs had feathers. You can maintain your images of scaly Stegosaurus, Diplodocus, and Edmontosaurus. Other headlines came closer to the truth: “Fuzzy fossil may indicate most carnivorous fossils had feathers“.
This second headline has a lot more basis in what the paper, published in PNAS, actually suggested. Previously, all the feathered dinosaurs discovered have been part of the same group, known as the coelurosaurs. A subset of the coelurosaurs are the Aves, the birds, which kind of makes sense: the group that birds developed from should be the group of dinosaurs with feathers and other bird-like characteristics. What is interesting about Sciurumimus is that is it not a coelurosaur, but a megalosaur, a different branch of theropod dinosaurs.
As you can see from the chart above, megalosaurids split off from the rest of the theropods pretty early on, near the base of the evolutionary tree. This means we have two options, based on the fact that both Scuirumimus and most of the coelurosaurs have feathers: either the megalosaurs and the coelurosaurs both evolved feathers independently, or feathers appeared in the theropod line before the megalosaurs took off on their own evolutionary path. Like skeptics use Occam’s Razor to parse down to the simplest explanation, evolutionary biologists use the principle of parsimony to trace the evolution of characteristics. It’s certainly possible that feathers arose multiple times independently, but it’s a lot simpler to say they evolved once, and are a basal characteristic of the carnivorous dinosaurs.
This new little dinosaur on its own provides some tantalizing hints, but isn’t enough to conclusively say that all theropods, much less all dinosaurs, were covered in downy coats. We’ll need to find many more feathered dinosaur specimens to answer that question once and for all. What it does do, however, is show just how rapidly changing the field of paleontology can be. I’ve talked before about how our conceptions of what dinosaurs looked like has changed remarkable in my 19 years. This is just another step on that path of discovery.
Featured Image from ScienceDaily