I admit it, nine-year-old me would have cried at the idea of Tyrannosaurus rex, my all-time favorite dinosaur, sporting a coat of feathers like a bird.
I first encountered the above illustration in an issue of National Geographic back at that tender age. The issue had a whole article on then-recent discoveries of dinosaur fossils sporting impressions of feathers from China, with numerous model reconstructions and other artwork depicting how the animals would have looked in life. Mind you, I was already aware that some theropod (or “meat-eating”) dinosaurs were close relatives of modern-day birds, and that the “first bird” Archaeopteryx demonstrated a visible link between the two groups. What the new Chinese fossils demonstrated was that the prevalence of feathers among theropods went beyond Archaeopteryx and its immediate ancestors and covered groups once thought to be scaled like other dinosaurs, such as dromaeosaurids (“raptors” such as Velociraptor and Deinonychus), oviraptorosaurs (Oviraptor), and compsognathids (a family including, well, the tiny Compsognathus).
Seeing Velociraptor, the intimidating antagonists of Jurassic Park, portrayed as feathered like birds was already enough to ruffle my feathers (pun very much chosen with intent). But the most offensive illustration in that issue by far, in my juvenile eyes anyway, was the one suggesting that Tyrannosaurus and its cousins in the tyrannosaurid family would have possessed a feathery coat as well. It didn’t matter that the illustration contrasted a downy hatchling with its scaled adult. The very idea of my favorite dinosaur, lord of the jungle of Late Cretaceous North America, ever having the telltale body covering of a lowly, cowardly bird seemed a major downgrade. It was heretical enough to put me off the idea that any dinosaurs evolved into birds at all.
Twenty years have passed, and I have matured enough to recognize that some so-called “non-avian” dinosaurs did, indeed, have feathers, and that all of today’s birds represent an offshoot of these dinosaurs. The preponderance of evidence so far does suggest that, contra the Jurassic Park movies, that dromaeosaurids like Velociraptor would have been feathered by default, as would the flock of Gallimimus seen in the first film’s stampede scene (at least as shown by new fossils of its cousin Ornithomimus). I cannot dispute this, nor do I even mind it anymore.
My feelings about feathered tyrannosaurs, on the other hand, have come full circle. Beginning in the early 2010s, I have warmed up to the idea and was eagerly drawing full feathered coats on them between 2012 and 2013. It was after that period of my life that my skepticism of the concept returned. In the years since, I have lost any remaining love for it and, if anything, have grown even more sick of it than I ever was as a child.
This time, however, I have good reason to believe that neither Tyrannosaurus rex nor the other members of the family Tyrannosauridae ever had feathers. And not only because they look better without them.
Before I tell you that story, however, I must tell you the one that gave feathered tyrannosaurs any appeal at all.
It was in 2004 that they uncovered a feathered dinosaur more closely related to tyrannosaurids than the others. This one too lived in China, during the Early Cretaceous Period around 126 million years ago, and its discoverers christened it Dilong paradoxus, meaning “surprising dragon”. Though only five feet in length, the skeletal remains associated with the impressions left behind by its downy feathers suggested that it represented a possible progenitor of Tyrannosauridae. To clarify, it was not classified as a tyrannosaurid itself, but as a member of a larger grouping called Tyrannosauroidea (note the “o” between the “i”) that included Tyrannosauridae. The implication there was that, much as humans once evolved from hairy apes, so too had tyrannosaurs evolved from feathered ancestors.
This, by itself, did not guarantee that tyrannosaurids proper retained those feathers later in the Cretaceous. Keep in mind that feathers on dinosaurs are thought to have evolved to keep their bodies warm, not to help them fly. Since larger warm-blooded animals can generate more body heat than they lose and retain more of it relative to their smaller counterparts, one could see larger tyrannosaurids like T. rex losing the feathery coats of their diminutive, Dilong-like ancestors, especially given the hothouse conditions of the Mesozoic world (during T. rex’s heyday in the Late Cretaceous, tropical to subtropical lifeforms like palm trees, bald cypress, and crocodilians were thriving as far north as Montana). This might also be why elephants and rhinoceros in the tropics today tend to have less body hair than either smaller mammals in the same regions or to their own cousins (the woolly mammoths and rhinoceros, respectively) in colder environments.
Enter Yutyrannus huali, another tyrannosauroid from Early Cretaceous China. Found in 2012, it too showed a coat of downy feathers like Dilong. The catch was that this was a much larger animal than Dilong, weighing up to one ton with a body length of thirty feet. While this dinosaur did seem to have preferred a cooler, more temperate climate than T. rex and its tyrannosaurid kin, paleontologist Thomas Holtz suggested that, since some tyrannosaurids did in fact range up into to the (then temperate) polar regions, it was possible that they too had feathers like Yutyrannus. Holtz’s reasoning was that, since tigers have furry coats whether they live in northeast or southeast Asia, why wouldn’t tyrannosaurids retain feathers as well?
It was around this period that I came to like — even prefer — the portrayal of feathered tyrannosaurs. It was attractive in a contrarian, even rebellious, way, and yet it had exploded in popularity within the paleoart community. Drawing feathered tyrannosaurs had become a trendy way to buck tradition, if you will.
There remained one small complication underlying this outgrowth of artistic enthusiasm for downy rexes, however. Namely, while we had all gotten excited about feather impressions on distant relatives of the tyrannosaurid dinosaurs, skin impressions from the Tyrannosauridae themselves — Tyrannosaurus rex included — told a fundamentally different, much scalier story. And, although the big report compiling this data came out in 2017, some of it had been mentioned in publications going back to 2003 (see the link’s list of citations). And we had chosen to neglect it all in our feather fervor!
Many of these scaled skin impressions had come from areas of the body known to have possessed feathery coating in earlier “tyrannosauroids” like Yutyrannus and Dilong. Of course, one could argue that the later tyrannosaurids could have still kept a “crest” of feathers running along the tops of their bodies, analogous to something like a horse’s mane, but evidence of this speculative structure remains to be found. What seems clear is that, at one point in their evolution, tyrannosaurids seem to have sacrificed most of the feathers on their bodies and then replaced them with pebbly scales like those of most other dinosaurs. In other words, their skin covering may represent an evolutionary reversion of sorts, a sign that evolution need not always run in one direction.
At least, that would have been the case if tyrannosaurids really had evolved from feathered tyrannosauroids in the first place. The problem is that we don’t know for sure whether this would have been the case at all. For example, some cladograms like the following(think of a cladogram as a form of evolutionary family tree) show primitive “tyrannosauroids” like Dilong and Eotyrannus as grouping with other feathered dinosaurs to the exclusion of Tyrannosauridae proper (represented below by Gorgosaurus and Tyrannosaurus). A more recent paper reports that, while dinosaurs of the family Proceratosauridae (the family which includes Yutyrannus) are often identified as part of Tyrannosauroidea, their own study found the proceratosaurid family branching away from the supposed tyrannosauroids towards more birdlike forms.
Since all of these studies assess the relatedness of dinosaurs through analyses of fossils’ anatomy rather than genetic analysis (dinosaur DNA of sufficient quality for study, unfortunately, would be very hard to come by), there will always remain a degree of uncertainty in their accuracy. But if there are grounds to doubt that Dilong, Yutyrannus, or their feathered relatives count as members of Tyrannosauroidea alongside the tyrannosaur family proper, it could mean that tyrannosaurs never had feathers. Their ancestors could have split away from those of all feathered dinosaurs before the latter grew their fluff in the first place.
This is not to say that the old depictions of tyrannosaurs, like the one in Jurassic Park, were accurate in entirety all this time. They may have gotten the scaly bodies right, but the skin covering their faces would be a different matter. More likely, it — and, for that matter, the facial texture of all dinosaurs — looked like that of modern crocodiles and alligators.
The evidence for this comes from a study on Daspletosaurus horneri, a smaller and earlier relative of T. rex. Analysis of its skull suggests that it would have been covered with a cracked “scaly” texture similar to that of crocodiles, with tiny touch-sensitive bumps sprinkled over the skin (it should be noted that crocodilians don’t have actual scales covering their faces like they do the rest of their bodies, but rather a cracked sheath of keratin over the head, which is the same substance that makes up birds’ beaks). This texture would have extended all the way to the gum line on the dinosaurs’ face, ruling out the presence of fleshy lips like you see on mammals.
Consider for a moment that, after birds, crocodilians are the closest living relatives of all dinosaurs, since they are both members of a larger reptilian clade known as the archosaurs. If tyrannosaurids had the cracked, lipless facial appearance of crocodilians, it might mean that they inherited that state from a common archosaur ancestor — which would by extension include the common ancestor of dinosaurs as a whole. In other words, before any dinosaurs evolved beaks like you see on birds, they wouldn’t have exhibit any of the cute facial expressions you see on the characters in The Land Before Time. Even the snake- or lizard-like sneers of Jurassic Park’s raptors would be unlikely. Instead, most of the dinosaurs would have smiled like crocodiles.
