We typically think of the fossil record as a black and white view into the prehistoric world, but some fossils show that dinosaurs, fish, early insects and even ancient plants were very colourful creatures indeed. A team led by Yale University paleogeologist Maria McNamara have analysed spectacularly coloured fossils of beetles that lived 15–47 million years ago—and these fossils have preserved not only shape and structure, but also the colours of the beetles’ exoskeletons. Many other fossils use pigment traces to generate colour, which bounces light off a chemical, but the beetles’ colours are far richer because they are generated through a phenomenon called structural colouration, in which light bounces off nanometre-scale surface geometries. By analysing the fossils under an electron microscope, McNamara and her team found that the colours had shifted slightly during the fossilisation process—specifically, they had been redshifted , so a blue beetle would have become slightly greener, and a yellow one would have become slightly oranger. After correcting for this shift, the team can envision the beetles’ flashy metallic exoskeletons just as they looked when they were alive. These colours also give clues about how the beetle lived, allowing the researchers to determined whether they served visual functions like thermo-regulation or communication.
(Image Credit: Wired)