Fossilised ink sac gives up its melanin secrets

Caroline Morley, online picture researcher

(Image: British Geological Society)

Melanins are one those groups of biological compounds that turn up everywhere - birds' feathers, squid ink and even human hair and skin. Cell structures that would have contained the pigment have also been detected in fossils, allowing researchers to reconstruct the plumage patterns of dinosaurs.

This photo shows a fossil from the UK that contains evidence of melanin. It is also from the time of the dinosaurs, 160 million years ago, but it is not from a vertebrate - it is a cephalopod's ink sac. John Simon at the University of Virginia in Charlottesville and colleagues identified eumelanin in this fossil in a form very similar to the ink found in modern-day cuttlefish, Sepia officinalis, that live in the Mediterranean, Baltic and North Seas. Eumelanin is a brownish-black form of melanin and is stored in a sac by cuttlefish and other cephalopods ready to squirt as a defence against predators.

Simon said of the similarities between the fossil and modern eumelanin: "It's close enough that I would argue that the pigmentation in this class of animals has not evolved in 160 million years."

Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1118448109

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