We love dinosaurs. But what did they actually look like? And how do we know? More and more, these questions aren’t just science’s business anymore. Art, film, and video games are bridging the gap between entertainment and science and let us explore how these ancient creatures may have behaved and what they looked like (and how many people they could eat if they were set loose in a theme park). Read on to find out how we know their actual colours and what colours can tell us about how they lived.
Ever since the first dinosaur fossils were discovered, the idea of giant beasts running around killing each other has fascinated adults and kids around the world, from the hallowed halls of science to your local nursery. Of course, science does its job and we now know a lot better (check out the Top 10 Cutest Dinosaurs), but the fascination with dinosaurs still stands: from Jurassic Park to Walking With Dinosaurs and the recent surge of video games such as Jurassic World: Evolution, Saurian and The Isle which allow you to fight them, ride them and keep them in a zoo (and yes, you can also run around and eat people if you wish to do so). The genre and its limitless possibilities in graphic design and animation not only produce beautiful images (see gallery below) but also have created a whole new demand for scientifically accurate reconstructions.
Slideshow: Snapshots from Jurassic World: Evolution. Source
Palaeontology has always been great for heated arguments between scientists. The idea that modern birds (just like that seagull that stole a chip from you once) are the descendants of dinosaurs was accepted fairly quickly, but how birds learned to fly is still a raging debate with no solution in sight. Birds have feathers, yes, but when did they evolve? Many protested at the concept of the giant Tyrannosaurus rex from Jurassic Park being covered in feathers like a 40ft long chicken, but in 2012, a new tyrannosauroid with primitive feathers up to 15cm in length was found, so maybe T. rex did have feathers?
Dinosaur feathers don’t just tell us about where modern birds might have come from. They can also give us some incredible detail about what the animal may have looked like and how it lived, as described in two recent publications by researchers at the University of Bristol and a group from Hong Kong, Beijing and the US in the brand new field of palaeocolour reconstruction, which aims to figure out what colour dinosaurs actually had and how their colour patterns are linked to their ecology (see here and here).
While feathers are not made out of bone and decay rather than fossilise, they can still leave impressions in the material surrounding the fossil and give us an idea of what they looked like compared to modern bird feathers and where on the body they were positioned – but these impressions can also tell us about their colours.
Because modern birds are dinosaurs, we often turn towards them when we try to understand the anatomy and ecology of extinct dinosaurs. There are many different pigments in bird feathers, the most important of which is melanin, which can also be found in human skin and produces a range of reddish, brown, grey and black colours. The exact colour depends on its molecular structure, but also the way it is packed together inside organelles called melanosomes (see below). These melanosomes are produced in cells called melanocytes and then distributed through the skin and into those cells that create structures like hair, horns and feathers. When researchers looked at the impressions of dinosaur feathers under an electron microscope, they found tiny structures that looked just like the melanosomes in modern birds.
The first fossil whose colouration was fully reconstructed based on the structure of these melanosomes was Anchiornis huxleyi, a small feathered dinosaur from the Late Jurassic of Liaoning, China (Li et al. 2010). While the body feathers showed elongated black melanosomes, the specimen had a crest of long feathers with shorter, reddish brown melanosomes – see below for the authors interpretation of what Anchiornis could have looked like according to its feathers.
Naturally, many colours in animals have a purpose. Be it to blend in with their surroundings to hide from predators or to attract mates, they can paint us a small picture of their world. For example, Sinosauropteryx and Psittacosaurus are two small dinosaurs from China that both exhibited countershading, a colour pattern seen in animals such as sharks and deer: their back is a lot darker in colour than their underside, and when light falls from above, the shadows help the animal blend into their surroundings. The optimal pattern depends on the light conditions in the environment, and when they were simulated under different light conditions (see below), the pattern of Sinosauropteryx would have been more suited to open landscapes, while Psittacosaurus could have lived in forests. All speculation? As it turns out, no: the types of rocks and fossil plants we have found around the Psittacosaurus fossil are typical for forest environments.
These new techniques help us understand prehistoric animals and landscapes, but how accurate are they? Honestly, we don’t quite know. Melanin is a very stable pigment, but many other colours like yellows and greens that we see in birds don’t preserve well, so our reconstructions may well be incomplete. Also, the number of fossils with preserved melanosomes is small, and another Anchiornis fossil didn’t show any red colouration (Lindgren et al. 2015) – was it a different species? Did males and females look different? We can’t know at this point, and this is the case for many questions. T. rex lived in subtropical forests where a full coat of feathers probably would have led to overheating, but until we find evidence that it didn’t have feathers, be prepared to see a video game appear where a 40 ft terror chicken will try to eat you.
References:
Lindgren, J., Sjövall, P., Carney, R. et al. Molecular composition and ultrastructure of Jurassic paravian feathers. Sci Rep 5, 13520 (2015).
Li Q., Gao KQ., Vinther, J., et al. Plumage Color Patterns of an Extinct Dinosaur. Science 327, 1369-1372 (2010)
Roy, A., Pittman, M., Saitta, ET. et al. Recent advances in amniote palaeocolour reconstruction and a framework for future research. Biol Rev 95, 22-50 (2020)
Vinther, J.: Reconstructing Vertebrate Paleocolor. Annu Rev Earth Planet Sci 48, 345-375 (2020)
Xu X., Wang K., Zhang K. et al. A gigantic feathered dinosaur from the Lower Cretaceous of China. Nature 484, 92-95 (2012)
The Quagga 