What colour were fossil animals?

Dr Michael Pittman of the Vertebrate Palaeontology Laboratory, Department of Earth Sciences, The University of Hong Kong led an international study with his PhD student Mr Arindam Roy that evaluates fossil colour reconstruction methods to propose a new study framework that improves and expands current practice. The paper was recently published in the journal Biological Reviews.

A pristine specimen of the feathered dinosaur Anchiornis huxleyi showing its colour patterns.
Melanin was first identified from an animal from this species [Credit: Xiaoli Wang]

"People are fascinated by the colour and pattern of dinosaurs and other extinct animals because these aspects can tell you so much about an animal. Just think of a zebra and a peacock. We evaluated everything we know about fossil and modern animal colour and used that knowledge to propose a framework to improve how we reconstruct fossil colour in the future." said Dr Pittman.

A life reconstruction of the feathered dinosaur Anchiornis huxleyi based on fossil evidence
of its colour and patterning. This evidence included inferences about melanin pigments
[Credit: HKU MOOC/Julius T Csotonyi/Michael Pittma]

Colour and patterns are critical to understanding the life, ecology, physiology and behaviour of animals. These colours are produced when light interacts with pigments and the structure of animal tissue. Common naturally-occurring animal pigments include melanin, carotenoids, porphyrins pterins, flavins and psittacofulvins which produce colours ranging from black and grey to yellow, orange and green.

Distribution of different colour-producing pigments among vertebrate animals. Covers fish, amphibians,
mammals, lizards, snakes, crocodilians and extinct archosaurs including non-avialan dinosaurs
 and birds. Dotted lines indicate stem groups; bold lines indicate crown groups
[Credit: HKU]

Feathered dinosaur fossils instrumental to understanding the origin of birds were the first animal fossils to yield evidence of melanin, the colour pigment we also have in our eyes and hair. In the last ten years, colour patterns have been reconstructed in over 30 fossil animals including birds, non-avialan dinosaurs and mammals, providing a unique opportunity to test ecological and behavioral hypotheses that were previously out of reach. Unfortunately, our knowledge of other pigments is scarce in the fossil record as these non-melanin pigments are more difficult to fossilise. This incomplete knowledge and the lack of a standard study approach have been prevailing challenges to the reconstruction of colour in fossil animals.