Camouflage quirks of parrot dinosaur revealed


What was thought to be bacteria on a fossil was actually pigment, allowing biologists to reconstruct this little dino's skin pattern. Amy Middleton reports.


VINTER ET AL. / CELL PRESS

The camouflage trick used by a parrot-like dinosaur to blend into its environment has been described by a new study, thanks to incredibly well-preserved fossils found in China.

Psittacosaurus is a cute horned dinosaur that lived during the early Cretaceous. Its name means ‘parrot lizard’ and references its beak. The species also sported scaly skin and long bristles extending from its tail.

The Psittacosaurus fossil in question, which had been on display at a museum in Germany for the past decade, displayed patterns thought to be dead bacteria.

But Jakob Vinther, a biologist at University of Bristol in the UK and lead researcher on the study, identified these patterns as remnants of melanin – the pigment that gives colour to skin, hair and scales.

This leftover melanin, which, incredibly, can be observed with the naked eye, appears in distinct colour patterns, which Vinther was keen to study.

According to Vinther and his international team, the pattern represents a common trick of camouflage known as countershading, in which an animal’s colouring moves from light to dark to match the gradual fading of light.

“The fossil preserves clear countershading, which has been shown to function by counter-illuminating shadows on a body, thus making an animal appear optically flat to the eye of the beholder,” Vinther explains.

Fossilised specimen of Psittacosaurus.
Vinter et al. / Cell Press

The fossil suggests Psittacosaurus had a light underbelly and tail, with more colour appearing on its chest and across its back. While some fish fossils have exhibited this trait, Psittacosaurus is the first terrestrial fossil to be connected with this form of camouflage.

Next, the researchers set about checking the effectiveness of this evolutionary trick. They created a 3-D, life-size model of Psittacosaurus and took two separate casts – on one, they projected the colour patterns left by the fossilised melanin; the other was painted uniform grey.

The researchers then observed how different light formations camouflaged the body of the dinosaur.

“By reconstructing a life-size 3-D model, we were able to not only see how the patterns of shading changed over the body, but also that it matched the sort of camouflage which would work best in a forested environment,” says co-author Innes Cuthill, also at University of Bristol.

Reconstruction of the parrot lizard Psittacosaurus in its forest habitat. It dark colours would have been well suited to areas with scattered light.
Vinter et al. / Cell Press

Because this form of countershading works best in forests, identifying this incredible trait also offered clues about the dinosaur’s habitat.

This finding could help experts predict the habitat of an extinct species, where colour pigments are well-preserved in fossils.

Countershading is found throughout the animal kingdom, including among primates. In some species of caterpillar, reverse countershading keeps the animal camouflaged while it hangs upside-down.

The finding was published this week in Current Biology.

Amy middleton.jpg?ixlib=rails 2.1
Amy Middleton is a Melbourne-based journalist.
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