FOR years you could only guess at what colour prehistoric beasts were.

But now a team that includes a Southampton scientist may have made a major breakthrough by revealing the colouring of long-extinct animals. Pigment preserved in fossilised skin from a 55 million-year-old leatherback turtle, an 85 million-year-old mosasaur and a 196–190 million-year-old ichthyosaur were analysed.

Dr Gareth Dyke, senior lecturer in vertebrate palaeontology at the University of Southampton, said: “The most sensational aspect of the investigation is that it can now be established that these ancient marine reptiles were, at least partially, dark-coloured in life, something that probably contributed to more efficient thermoregulation, as well as providing means for camouflage and protection against harmful UV radiation.”

The results of the study by scientists from Denmark, England, Sweden and the USA are presented in the scientific journal Nature.

The analysed fossils are composed of skeletal remains as well dark skin patches containing masses of micrometre-sized, oblate bodies.

These microbodies were previously interpreted to be the fossilised remains of those bacteria that once contributed to the decomposition and degradation of the carcasses. But by studying the chemical content of the soft tissues, the scientists were able to show that they are in fact remnants of the animals’ own colours, and that the micrometre-sized bodies are fossilised melanosomes, or pigment-containing cellular organelles.

If their interpretations are correct, then at least some ichthyosaurs were uniformly dark-coloured in life, unlike most living marine animals.