“INTRIGUINGLY, ALL OF THESE MORE BRIGHTLY COLOURED DINOSAURS LIVED IN THE TREES”
2 a russet head-crest on the crow-sized, four-winged, flying dinosaur Anchiornis.
These discoveries relied on a method developed in part by Vinther for determining the colour of dinosaur and prehistoric bird feathers, not based on chemical traces of the melanin pigment (as with Borealopelta), but on the shape of fossilised microstructures in the feathers called melanosomes.
These t iny, durable st ructures are packages of melanin that are also found in the feathers of modern birds, and the hair and fur of mammals. Conveniently for palaeontologists, the shape of the melanosomes in modern animals tends to correlate to their colourings. Reddish phaeomelanin, for example, is typically found in melanosomes that are round and 400-500 nanometres wide. Black or brown ‘eumelanin’ is packaged in 300nm sausage-shaped melanosomes. This means that, even though l it t le actual melanin remains in many of these fossils, researchers are still able to study the melanosomes and make reasonable guesses about the colour of these dinosaurs.
Using these techniques, we now know that early bird Archaeopteryx was black and white. Microraptor, the fourwinged dinosaur from China, has melanosomes that suggest not only a blue-black colouration, but also a beautiful sheen, similar to a Eurasian magpie or a crow. The duck-sized Caihong was potentially even more stunning, with the colourful iridescence seen in modern hummingbirds (see ‘How it works: Colouring in a dinosaur’).
The intriguing thing about all of these more brightly coloured dinosaurs is that they lived in the trees. “If you live in more shaded environments then you’re less exposed, both as predator and prey, and can become more colourful,” says Vinther. So, in these animals, bright colours may have been used in sexual displays to attract mates and intimidate rivals.
On the ground, however, it was a different story. Dinosaurs such as Sinosauropteryx, Borealopelta and Psittacosaurus would have been more exposed and vulnerable, so their colouring was more camouflaged and drab, Vinther argues. It’s likely that their dinosaur predators would have had excellent vision. Modern birds (the descendants of the dinosaurs) have some of the best eyesight in the animal kingdom, and can see ultraviolet light on top of all the colours that we see.
“You really had to be well camouflaged to stay alive, and camouflage strategies had to be more precise,” says Vinther, explaining why countershading may prove to be the norm for all but the largest and scariest ground-dwelling dinosaurs. This countershading was probably patterned – rather than the uniform greys, greens and browns that dinosaurs historically
Dr Maria McNamara was part of the team that found evidence of feathers and melanosomes in pterosaurs