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How colour shaped dinosaurs’ lives

The Week logo The Week 2019-09-04 James Ashford
a person riding a dinosaur in front of a car © Provided by Dennis Publishing Limited

Researchers studying dinosaur fossils have discovered that the colours of the ancient animals may have been radically different than previously believed.

And while exactly what those colours may have been has yet to be determined for most dinosaur species, the new findings suggest that pigment-producing structures go beyond how they looked and may have played a fundamental role inside their bodies too.

Palaeobiologists at University College Cork (UCC) found colour-controlling melanin in melanosomes - tiny structures found in animal cells - throughout dinosaurs’ bodies.

Melanin is the pigment that gives external organs and tissue such hair and eyes their colour. Skin is darker when there are higher levels of melanin, which is also believed to provide a barrier against UV damage caused by the Sun’s rays.

Scientists believe that external melanosomes could be the key to more accurately reconstructing the appearance of fossilised birds, reptiles and dinosaurs - and the discovery of the melanin-containing structures internally suggests they may reveal further characteristics as well.

“We’ve found it in places where we didn’t think it existed,” said Dr Maria McNamara, who co-led the new research - outlined in a paper in the journal Proceedings of the National Academy of Sciences of the United States of America.

“We’ve found melanosomes in lungs, the heart, liver, spleen, connective tissues, kidneys. They’re pretty much everywhere.”

The chemical signatures of melanosomes were different according to which organ they came from, meaning scientists may be able to map the inner tissue of ancient vertebrates.

The discovery of melanin in internal tissue suggests “intimate links” with dinosaurs’ metabolism and regulation of the chemical and physical state of their bodies.

The findings also raise questions about melanin’s function in other animals - including humans.

“There’s the potential that melanin didn’t evolve for colour at all,” said McNamara. “That role may actually be secondary to much more important physiological functions.”

Other researchers agree that there is more to animal colour than visual means such as signalling, mating and camouflage, says Horizon magazine.

“For example, how do colours affect thermoregulation? Flight? Such functions may be complementary to, or even more significant, than purely visual functions,” said Dr Matthew Shawkey, an evolutionary biologist at Ghent University in Belgium.

Dr Steve Brusatte, a vertebrate palaeontologist and evolutionary biologist at the University of Edinburgh, said: “What started as a novelty of deciphering dinosaur colours has turned into a very serious field which is studying the origins of key pigment systems.”

It could reveal “how the evolution of colourful structures may have helped drive major evolutionary transitions like the origin of flight, and how colour is related to ecology and sexual selection”, added Dr Brusatte.

New synchrotron X-ray techniques were used by scientists to analyse the chemical make-up of fossils, revealing the never-before-seen internal melanin.

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