Dinosaur coloration
Dinosaur coloration is generally one of the unknowns in the field of paleontology, as skin pigmentation is nearly always lost during the fossilization process.
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.
[4] 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.
[7] 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.
[12] In 2010, a team of researchers analyzed the holotype remains of Sinornithosaurus (IVPP V12811) and other feathered dinosaurs from the Yixian and discovered melanosomes.
A 2017 study by Smithwick et al. also reported that the body coloration of Sinosauropteryx extended to the face, creating a raccoon-like "mask" around the eyes.
[15] In a 2020 study, Eliason and Clarke determined that the feathers on the head, tail, and wing primaries of the Eocene lithornithid Calciavis were iridescent, likely glossy black.
[16] In their 2016 description of the Early Cretaceous ornithuran bird Changzuiornis, Huang et al. noted melanosomes indicative of black coloration in the fossilized feathers of the wings and leg/tail region.
[18] In 2018, Li et al. reported extensively preserved melanosomes and plumage patterns in the fossilized feathers of another specimen (CUGB P1401) of a species of Confuciusornis.
[19] Structures believed to be fossilized melanosomes were found in five feather samples from the only known specimen of the enantiornithean bird Cruralispennia using scanning electron microscopy.
High aspect ratios have been known to correlate with glossy or iridescent colours, although without knowing the structure of a feather's keratin layer (which does not fossilize well), no hue can be assigned for certain.
Ksepka et al. tested the feathers on the top of the head for preserved melanosomes, and noted densely-packed, rod-like eumelanosomes, which typically create iridescent black colours.
[24] Wang et al. (2018) analyzed the elongate, closely-spaced melanosomes preserved in the feathers of a specimen of the Early Cretaceous ornithurine Iteravis to determine that they were likely black in colour.
[26][10] In 2019, Musser, Ksepka & Field determined that a long feather from the tail of the Eocene bird Pellornis would have been a black-brown colour.
[28] In their 2021 description of the Early Cretaceous pengornithid Yuanchuavis, Wang et al. described the presence of eumelanosomes in the preserved tail feathers.
[30] A 2017 examination of melanosomes preserved in a specimen of Borealopelta indicated that the nodosaurid had a reddish-brown coloration in life, with a counter-shaded pattern that may have been used for camouflage.
This discovery may indicate that Borealopelta was under threat of predation, despite its large size, and that the armor on its back was primarily used for defensive rather than display purposes.
[31] A 2020 examination of a sample of 3D preserved fossil skin (YPMPU 016969) from the flank of a hadrosaurid revealed the presence of eumelanin in the specimen.
This is similar to that of many modern species of forest-dwelling deer and antelope and may be due to a preference for a densely forested habitat with low light.
