What Color Dinosaurs Were
Remember drawing dinosaurs in grade school, when the teacher would tell you to use any color you like, because we’ll never know for sure what these amazing prehistoric beasts looked like? Forget that shit.
Meet Psittacosaurus. This little guy lived in what is now China during the early Cretaceous period, which spanned from 145 to 100 million years ago. Today, thanks to the discovery of fantastically preserved fossils and technological advancements, we have a very good idea what he looked like — right down to the color.
A research team unveiled this week what they contend is the most lifelike full-size model of a dinosaur ever created. Their study on the animal’s coloring and camouflage will be published in the September issue of Current Biology.
“I am not sure that many palaeontologists would have said we could find color in dinosaurs before 2008, but here we are,” Jakob Vinther, a paleobiologist with the University of Bristol and lead author of the research, tells Inverse in an email.
While he was a grad student at Yale, Vinther discovered that melanosomes, which are organelles present in the cells of birds and mammals and are responsible for pigmentation, could be preserved in some dinosaur fossils. Previously, researchers thought these structures were some sort of bacteria or other debris contaminating the fossil.
What made the discovery of fossilized melanosomes particularly revolutionary is that the shape of the melanosome itself dictates the color of the pigment it produces. By comparing these structures in fossils to those in birds and mammals alive today, scientists can work out not only the intensity of pigmentation but color, as well.
Most of the coloration studies done since then have been done on feathered dinosaurs, which are closely related to birds, allowing for a relatively easy comparison. This has allowed researchers to determine, for example, that Anchiornis had a red-crested head topping its white, black, and grey feathered body.
It’s still a matter of debate as to how complete a picture we can get of dinosaur coloration by looking at fossilized evidence of melanosomes, especially for those outside the group that includes all living birds. Today’s reptiles use chromatophores, not melanosomes, for pigmentation, and it’s possible that some dinosaurs had these as well. Also, some birds, like flamingos, derive additional pigmentation from the food they eat.
Still, when it comes to this particular fossil, the researchers are feeling confident that they’ve gotten it pretty damn close.
Psittacosaurus is an early cousin of Triceratops and other ceratopsians. Its name means “parrot lizard,” for its oddly endearing little beak, although that is not an indication of a close relationship to birds.Psittacosaurus has the distinction of being the dinosaur genus with the most species to its name, with the exception of living birds. An enormous wealth of these little herbivores have been found in China, Mongolia, and Russia. They could grow to about the size of a medium sized dog.
The specimen central to this research, which has yet to be assigned to a species, has a particularly compelling story to tell. It’s a small one, measuring under three feet from end to end. This was the firstPsittacosaurus, a creature known to have strange, spiky bristles along the section of its tail. But for a long time, scientists couldn’t really study the fossil despite its existence — it was being passed around between private owners in Europe, and no one knew where to find it.
Even if they could track down the owner, most paleontological journals won’t accept articles based on specimens in a private collection, because there’s no guarantee of access for scientists for replication or further study. At one time, this fossil was a central exhibit in the debate over whether dinosaurs should be bought and sold commercially at all, which rages on to this day.
Fortunately, the Senckenberg Museum in Germany ultimately scooped up the amazing find, and it has been on display there for the past 12 years. Those bristles probably were used in social and sexual display, like the mane of a lion or the spectacular plumage of some birds, Vinther and colleagues suggest in a separate study, published last month in Palaeontology. This is consistent with findings thatPsittacosaurus and other ceratopsians were social animals who lived in groups, and probably fought within their species over territory and mates.
This fossil is spectacular not only for its bristles, but for the skin preservation, which appears to show traces of the animal’s pigmentation. The spotting and shading are so vivid, it’s easy to imagine the real creature that lived and died before being crushed into this flat impression.
Easy to imagine, but to get that image accurate and right? For that, you need a team of experts. Vinther called on the authority of Robert Nicholls, a paleoartist, to take all the scientific evidence from the fossil itself and use that information to bring Psittacosaurus into the 3D world. Nicholls built a life-size model of the animal, and then painted it in, using his expertise in dinosaur reconstructions to fill in the blank for areas where skin impressions were not preserved.
This is a rare instance where paleoart is brought into the scientific process, rather than being tacked on after the research is finished. However, more and more paleontologists are recognizing how important art is, not only to imagining extinct creatures, but to discovery itself. “This is one of the most perfect marriages in which the paleoart is the key aspect of the scientific enquiry, which is also why the artist is a co-author,” says Vinther. “Paleoartists in general are super important as they help us convey our observations and bring these extinct animals to life. Often, their art and the process of making it makes us look at the fossils again and discover new things.”
The finished model appeared to have a very common sort of camouflage called countershading. This is when the parts of an animal that are typically in shadow are more lightly colored, and the result is that the creature appears flat against the background, making it harder for predators to make out their shape.
The ideal countershading pattern depends on the environment where an animal lives. If it spends its days in direct sunlight, the creature will likely be very dark on top, with a sharp contrast to lighter areas on the sides and belly. For animals that live in diffuse light environments, like forests, the countershading is softer and more graduated.
To investigate this question in Psittacosaurus, the researchers built a second model and painted it uniformly gray. They then photographed it in open and shaded environments to determine the ideal countershading for each. Amazingly, the painted Psittacosaurus model’s coloring very closely matched the ideal countershading for diffuse light.
“As we show with its color patterns, it lived in a forest,” says Vinther. “Fossil evidence of tree trunks and leaf fossils as well as pollen demonstrate that this forest was a coniferous forest with some ginkgos. Flowering plants had still not diversified to become the most dominant group yet.”
Amazingly, this new insight on what Psittacosaurus looked like tells us where and how it lived, too. “It was an herbivore and probably ate ferns and cycads,” he says. “Since it was a small herbivore, it was at the bottom of the food chain and thus there was a strong selective pressure for the least conspicuous psittacosaurus to survive, which is what we have documented with our fossil.”
Now that we can decode the color of (some) dinosaurs, what’s left to discover? Vinther says he’s not sure what the next frontier in paleontology will be, but he’s looking forward to finding out. “I hope that we discover a new site with dinosaur fossils preserving soft tissues that are a tad older than the ones that we have now, perhaps something from the middle or lower Jurassic.”