The research, led by University College Cork palaeontologist Maria McNamara, discovered new sources of the pigment melanin that will see scientists reexamine how they reconstruct the colour of fossil birds, reptiles, and dinosaurs.
“It’s absolutely critical that we understand the origins of melanosomes in fossils if we want to produce accurate reconstructions of the colours of ancient animals,” Dr McNamara said.
The team studied internal tissues in modern frogs with powerful microscopes and chemical techniques to show that internal melanosomes are highly abundant.
“This means that these internal melanosomes could make up the majority of the melanosomes preserved in some fossils,” said Mike Benton from the University of Bristol, who also collaborated on the project.
The team also used decay experiments and analysed fossils to show that the internal melanosomes can leak into other body parts during the fossilisation process, “like snowflakes inside a snow globe”, according to another collaborator on the project, Patrick Orr from University College Dublin.
There is a way, however, to tell the difference between melanosomes from internal organs and the skin.
“The size and shape of skin melanosomes is usually distinct from those in internal organs,” Dr McNamara said.
“This will allow us to produce more accurate reconstructions of the original colours of ancient vertebrates.”
Many recent studies of fossil colour have assumed fossilised granules of melanin — melanosomes — come from the skin.
However new evidence shows that other tissues — such as the liver, lungs, and spleen — can also contain melanosomes, suggesting that fossil melanosomes may not provide information on fossil colour.
The team used a unique chemical process for detection of melanin in modern and fossil materials developed by collaborators Kazumasa Wakamatsu and Shosuke Ito from Fujita Health University in Japan.
Dr McNamara was also helped in her research by her PhD student, Valentina Rossi, as well as an international team of palaeontologists from Britain and Japan.
Full details of the study will be published today in the journal Nature Communications.