The original colour of a fossil mammal which soared above the Earth 50 million years ago has been discovered by scientists for the first time.
Researchers combined morphological, experimental & chemical techniques to determine the colour of two species of bat, which lived in the Eocene Epoch, 56-33.9 million years ago.
They discovered that the bats were reddish-brown in colour by studying microscopic spherical & oblong-shaped structures in the fossils.
Scientists have previously been divided on whether such structures can be used to infer colour, or are simply fossilised bacteria that ate at an animal before it was buried.
In the study, researchers found that the organic microbodies in the skin, hair, feathers & eyes of exceptionally preserved fossils contain the remnants of melanin.
Melanin is the pigment that gives skin, hair & eyes their colour. It comes in two distinct colours – reddish brown phaeomelanin & black eumelanin.
Dr Jakob Vinther, of the University of Bristol, said: "This is a tremendous leap forward in our understanding of how fossils are preserved. We now know how melanin is preserved & we have the methods to confidently detect it.
"Very importantly, we see that the different melanins are found in organelles of different shapes: reddish melanosomes are shaped like little meatballs, while black melanosomes are shaped like sausages.
"We can see that this trend is moreover present in the fossils.
"This means that the correlation of melanin colour to shape is an ancient invention, which we can use to easily determine colour from fossils by simply looking at the melanosome shape."
The scientists replicated the conditions under which the fossils formed using high pressure, high temperature autoclave experiments to identify the origin of the structures.
They showed that the fossils contained fossilised melanin by using Time-of-flight secondary ion mass spectroscopy (TOF-SIMS), which had changed in chemical composition over time.
The two different types of melanin are moreover chemically different.
By using both lines of evidence, the team was able to determine that the two species of 50-million-year-old bat were both originally a reddish brown colour.
Caitlin Colleary, a PhD student at Virginia Tech who worked on the research, added: " We have now studied tissues from fish, frogs, & tadpoles, hair from mammals, feathers from birds, & ink from octopus & squids.
"They all preserve melanin, so it's safe to say that melanin is all over the place. Now we can confidently fill in some of the original colour patterns of these ancient animals."
The study is published in Proceedings of the National Academy of Sciences (PNAS) today.
Research for it was carried out at the University of Bristol & the University of Texas at Austin, supported by funds from UT Austin, National Geographic & the University of Bristol.