What Did Dinosaurs Really Look Like?

How Paleontologists Determine the Color of Dinosaur Skin and Feathers

pegomastax
A fanciful illustration of the newly discovered Pegomastax (Tyler Keillor).

In science, new discoveries are often interpreted within old, outmoded contexts--and nowhere is this more evident than in how the early paleontologists of the 19th century reconstructed the appearance of dinosaurs. The earliest dinosaur models displayed to the public, at England's famous Crystal Palace exposition in 1854, depicted Iguanodon, Megalosaurus and Hylaeosaurus as looking very much like contemporary iguanas and monitor lizards, complete with splayed legs and greenish, pebbly skin.

Dinosaurs were clearly lizards, the reasoning went, and so they must have looked like lizards as well.

For over a century afterward, well into the 1950's, dinosaurs continued to be depicted (in movies, books, magazines and TV shows) as greenish, scaly, reptilian giants. True, paleontologists had established a few important details in the interim: the legs of dinosaurs weren't actually splayed, but straight, and their once-mysterious claws, tails, crests and armor plates had all been assigned to their more-or-less correct anatomical positions (a far cry from the early 19th century, when, for example, the spiked thumb of Iguanodon was mistakenly placed on its nose).

Were Dinosaurs Really Green-Skinned?

The trouble is, paleontologists--and paleo-illustrators--continued to be fairly unimaginative in the way they portrayed dinosaurs. There's a good reason why so many modern snakes, turtles and lizards are drably colored: they're smaller than most other terrestrial animals, and need to blend into the background so as not to attract the attention of predators.

But for well over 100 million years, dinosaurs were the dominant land animals on earth; there's no logical reason they wouldn't have sported the same bright colors and patterns displayed by modern megafauna mammals (such as the spots of leopards and the zig-zag stripes of zebras).

Today, paleontologists have a firmer grasp of the role of sexual selection, and herd behavior, in the evolution of skin and feather patterns.

It's entirely possible that the huge frill of Chasmosaurus, as well as those of other ceratopsian dinosaurs, was brightly colored (either permanently or intermittently), both to signify sexual availability and to out-compete other males for the right to mate with females. Dinosaurs that lived in herds (such as hadrosaurs) may have evolved unique skin patterns to facilitate intra-species recognition; perhaps the only way one Tenontosaurus could determine the herd affiliation of another Tenontosaurus was by seeing the width of its stripes!

What Color Were Dinosaur Feathers?

There's another strong line of evidence that dinosaurs weren't strictly monochromatic: the brilliantly colored plumage of modern birds. Birds--especially birds that live in tropical environments, like the Central and South American rain forests--are some of the most colorful animals on earth, sporting vibrant reds, yellows and greens in a riot of patterns. Since it's pretty much an open-and-shut case that birds descended from dinosaurs, you might expect the same rules to apply to the small, feathered theropods of the late Jurassic and Cretaceous periods from which birds evolved.

In fact, in the last few years, paleontologists have succeeded in recovering pigments from the fossilized feather impressions of dino-birds like Anchiornis and Sinosauropteryx.

What they've found, unsurprisingly, is that the feathers of these dinosaurs sported different colors and patterns, much like those of modern birds, though of course the pigments have faded over the course of tens of millions of years. (It's also likely that at least some pterosaurs, which were neither dinosaurs nor birds, were brightly colored, which is why South American genera like Tupuxuara are often depicted as looking like toucans).

Yes, Some Dinosaurs Were Just Plain Dull

Although it's a fair bet that at least some hadrosaurs, ceratopsians and dino-birds sported intricate colors and patterns on their hides and feathers, the case is less open-and-shut for larger, multi-ton dinosaurs. If any plant-eaters were plain grey and green, it was probably giant sauropods like Apatosaurus and Brachiosaurus, for which no evidence (or presumed need for) pigmentation has been adduced.

Among meat-eating dinosaurs, there's far less evidence for coloration or skin patterns on large theropods like Tyrannosaurus Rex and Allosaurus, though it's possible that isolated areas on these dinosaurs' skulls were brightly colored.

Today, ironically, many paleo-illustrators have veered too far in the opposite direction from their 20th-century forebears, reconstructing dinosaurs like T. Rex with bright primary colors, ornate feathers, and even stripes. True, not all dinosaurs were plain grey or green, but not all of them were brightly colored, either--the same way that not all the birds in the world look like Brazilian parrots. One franchise that has bucked this garish trend is Jurassic Park; even though we have plenty of evidence that Velociraptor was covered with feathers, the movies persist in depicting this dinosaur (among numerous other inaccuracies) with green, scaly, reptilian skin. Some things never change!