Dinosaur coloration is generally one of the unknowns in the field of paleontology, as skin pigmentation is nearly always lost during the fossilization process. However, recent studies of feathered dinosaurs and skin impressions have shown the colour of some species can be inferred through the use of melanosomes, the colour-determining pigments within the feathers.
Feathered dinosaurs
Anchiornis
In 2010, paleontologists studied a well-preserved skeleton of Anchiornis, an averaptoran from the Tiaojishan Formation in China, and found melanosomes within its fossilized feathers. As different shaped melanosomes determine different colours, analysis of the melanosomes allowed the paleontologists to infer that Anchiornis had black, white and grey feathers all over its body and a crest of dark red or ochre feathers on its head.
In 2015, another specimen was reported to possess melanosomes that induced grey and black coloration, but no red or brown coloration. This may have been because of different testing methods or a different age or species of the second tested specimen.
Archaeopteryx
In 2012, Ryan Carney and colleagues produced the first colour study on an Archaeopteryx specimen. Fossilized melanosomes suggested a primarily black coloration in the feathers of the specimen. The feather studied was likely a covert, which would have partly covered the primary feathers on the wings. Carney pointed out that this is consistent with the flight feathers of modern birds, in which black melanosomes have structural properties that strengthen feathers for flight.
In 2013, a study published in the Journal of Analytical Atomic Spectrometry by Manning et al. reported new analyses on the feather revealing that Archaeopteryx may have had light and dark coloured plumage, with only the tips of the feathers being primarily black instead of the entire feather. Whether or not this coloration was primarily for display or flight is currently unknown.
A follow-up study by Carney and colleagues in 2020 suggested that the feather was matte black, not iridescent, with 90% probability, owing to the less elongated shape of the melanosomes. However, they noted that some of the melanosomes preserved three-dimensionally in the specimen were distorted to give the impression of iridescent melanosomes. Unlike Manning and colleagues, they reconstructed the feather as being completely dark at the tip.
Beipiaosaurus
Beipiaosaurus had a dense covering of downy-like fibers along with a secondary coat of longer, simpler feathers. In a study of the colour and shape of fossilized melanosomes in numerous extant and fossil specimens, Li et al. (2014) found that the preserved feathers in the neck area of the Beipiaosaurus specimen implied brownish and dark brownish coloration.
Caihong
The fossilized feathers of Caihong possessed nanostructures which were analyzed and interpreted as melanosomes. They showed similarity to organelles that produce a black iridescent colour in extant birds. Other feathers found on the head, chest, and the base of the tail preserve flattened sheets of platelet-like melanosomes very similar in shape to those which create brightly coloured iridescent hues in the feathers of modern hummingbirds. However, these structures are seemingly solid and lack air bubbles, and thus are internally more akin to the melanosomes in trumpeters than hummingbirds. Caihong represents the oldest known evidence of platelet-like melanosomes.
Caudipteryx
In the 1998 description of Caudipteryx, Qiang et al. noted the existence of preserved colour bands on the fossilized tail feathers of the holotype specimen. Later studies indicated that the body feathers of Caudipteryx contained eumelanin, a pigment lending dark grey/black shades.
Microraptor
In 2012, Quanguo Li and colleagues analyzed BMNHC PH881, a specimen of Microraptor, and determined that the coloration of typical Microraptor feathers was iridescent black. The melanosomes were narrow and arranged in stacked layers, reminiscent of the blackbird. It was believed that Microraptor was nocturnal due to size of the scleral ring. However, the iridescent nature of its feathers has cast this into doubt, since no modern birds with iridescent plumage are known to be nocturnal.
