Feathers for Tyrannosaurs
Feathery dinosaurs can be an acquired taste. Not everyone likes seeing animals that have traditionally been wrapped in scales begin to sprout brightly-colored plumage, especially when such changes threaten to dispel the menacing appearance of Hollywood dinosaur villains like Jurassic Park‘sVelociraptor. Of course, alterations to some dinosaurs raise the dander of fossil aficionados more than others. A fluffy Siats will stir debate among experts, but, simply by dint of the dinosaur’s celebrity, the prospect of a fuzzy tyrannosaur is a pop culture flashpoint in the tussle between dinosaurs of our childhood and the animals science is uncovering.
The impending release of Walking With Dinosaurs 3D has put tyrannosaur feathers on my mind again. The Land Before Time it ain’t, but the gorgeously-rendered animated film will undoubtedly excite the latest generation of young dinosaur fans. That’s why many paleontologists and dinosaur fans are disappointed that CGI docudrama’s villains, a gaggle of iridescent Gorgosaurus, are devoid of any fluff or fuzz.
In the grand scheme of the tyrannosaur family tree, Gorgosaurus was a large, sleek, and agile member of a subgroup called tyrannosaurids. This is the category of the most famous tyrant dinosaurs, including Tyrannosaurusitself. Yet we know relatively little about what the outside of these dinosaurs looked like. There are some rumored skin impressions – some lost, others frustratingly unpublished – that show tyrannosaurids had pebbly scales, at the very least. Befitting the traditional view of dinosaurs as scabrous reptiles, the filmmakers decided to go the conservative route and reviveGorgosaurus sans fluff.
Body size has played into the argument for scaly tyrannosaurids, too. If a 30 foot long, two ton plus Gorgosaurus had an active, hot-running metabolism, then wouldn’t an insulating coat of fluff cause the predator to overheat? Scale supporters could concede that small tyrannosaurs, and maybe even tyrannosaurid chicks, had fluff, but the prospect of a heat-addledTyrannosaurus has helped keep large tyrannosaurs scaly.
Enter Yutyrannus. Not long after the Walking With Dinosaurs 3D settled on their scaly Gorgosaurus, paleontologist Xu Xing and colleagues described a roughly 30 foot long, one and a half ton tyrannosauroid that wore an expansive coat of protofeathers. Yutyrannus, along with some experimental work on how large animals shed body heat, suggest that body size was not a barrier to being a fluffy dinosaur.
Yutyrannus was described too late to change the look of Hollywood’s latest take on Gorgosaurus. And fans of the scaly-skinned model are often quick to point out a relational barrier between the two dinosaurs. The 125 million year old Yutyrannus was an archaic from categorized as a tyrannosauroid, while Gorgosaurus was a later and more derived member within the tyrannosaurid subgroup. Since the only tyrannosaurs so far discovered with protofeathers are the tyrannosauroids Yutyrannus and the comparatively tiny Dilong, and tyrannosaurids only left behind scaly skin, then maybe tyrannosaurs shed their simple plumage over evolutionary time.