How the dino got its shading

27 September 2016

Interview with

Dr Jacob Vinther, The University of Bristol

Scientists from the University of Bristol have revealed the most accurate Reconstruction of the Psittacosaurusreconstruction of a dinosaur ever made. A fantastically preserved fossil, found in a lake deposit in China has revealed the colouring of the creature, but also where it lived before it found itself at the bottom of the lake. Georgia Mills spoke to researcher  Jakob Vinther  from the University of Bristol, to get to know this cretaceous character..

Jakob - Well the dinosaur is called "psittacosaurus" which means the parrot lizard. The derivation of the name comes from the fact that it's got a beak that kind of looks like a parrot's beak. So this is a distant relative to triceratops and it's about the size of a labrador, and it's from some deposits in northeastern China in the province called Liaoning that we find these fossils in, which is about one hundred and twenty million years old.

Georgia - I looked at some of the reconstructions of this dinosaur from your paper and it's quite cute. It's got these little sort of cheek horns that stick out at the sides and it looks like quite a friendly vegetarian.

Jakob - Yes, this dinosaur was definitely extremely cute. Now that we finally have a reconstruction of what this dinosaur looked like we can see that it's exorbitantly cute. It kind of looks like somewhere between like maybe E.T. and then I don't know what else you can compare it with. It kind of like looks like E.T. - it's got a very cute, wide face but then it has these very wide cheek horns that make it look very, very distinct.

Georgia - And what have you been investigating for this dinosaur?

Jakob - We have been looking at a fossil of this psittacosaurus which is extremely well preserved. What we have is remains of the skin associated with the skeleton and psittacosaurus is a fairly common fossil in these deposits in northeastern China. But occasionally we get some of these specimens that got washed out into these lake deposits and this one is really, really complete and really, really well preserved.

So we have looked at these skin impressions and we find organic residues in these.  And we've recently discovered when we have organic remains, for example, feathers preserved in dinosaurs, we had the pigments retained in these and we can look at these pigments, which is melanin, and make some inferences about the original colours and colour patterns that this dinosaur would have had. So now we've done the same thing with this dinosaur, we have looked at these organic residues and when we look at them under a so-called scanning electron microscope, then we find little structures which are melanosomes. So that demonstrates what we have preserved in this fossil is the melanin pigment that gave the colour to the animal.

Georgia - OK. So you've actually found the fossilised remains of pigments and that has then, in turn, informed you of what this dinosaur's colouring looked like. So what can this tell you about the dinosaur other than helping you having these lovely reconstructed paintings of it?

Jakob - So that's the interesting thing - we can also say something about what this dinosaur was doing because it had these colour patterns for a reason and these colour patterns that we see in this dinosaur are various types of camouflage patterns. And the most important one, which is the one we best can use to say something about the environment that it lived in is this transition in light to dark between the back, and the belly, and the tail of the animal, which is this pattern called "countershading."

Georgia - So, putting everything together, and we've got a labrador sized dinosaur, it's got a body like a kind of chubby t-rex, and the head looks confusingly like a cross between ETs and a parrot. Also there's some weird grass looking stuff sticking out of it's tail. And then the colouring is this speckled black and red on a tan body, which is much darker on the top and this is what Jakob referred to as countershading.

Countershading is a clever technique that's still used by animals today. It involves having a lighter underside and a darker back. Think about things like penguins, deer, rabbits - they all have lighter bellies and this basically makes you look a lot less conspicuous. Our brains are trained to spot objects when they are lighter on the top and darker on the bottom as that's how the sun tends to light things up. But, if you counteract this with your shading - countershading - you tend to appear more flat and this makes it easier to avoid being eaten as predators have a harder time spotting you.

So this dinosaur seems to have been using this trick over a hundred million years ago and this also tells us something about its environment.

Jakob - Because what we see in living animals is that the countershading varies depending on the habitat that they live in. And the reason why is because the light conditions will vary depending on where you live. So the countershading in animals that live in savannas, for example, are usually sitting very high on the body and they're very sharp. Whereas animals that live in a forest, they have a countershading which is much more gradual and it sits much further down on the body.

So, basically, it means that we can use this sort of evidence to go back to reconstruct this dinosaur and put the original colour patterns onto it and we can show that it lived in a habitat which was a forest.

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