Melanosomes are melanin-containing organelles found in the feathers of birds, and responsible for the colors of those feathers. Researchers looked at the fossils of several non-avian dinosaur species possessing integumentary filaments which had previously (and controversially) been categorized as feathers. The controversy stemmed from the classification of these filamentous structures as feathers, with some researchers contending that the structures were degraded dermal collagen fibers, and not feathers at all.
Seeking to resolve this issue, Zhang et al examined the fossils using a scanning electron microscope, finding evidence of "sub-micrometre-sized bodies" that they interpret as fossilized melanosomes. Furthermore, the researchers identify the specific color associated with the fossilized melanosomes: a reddish-brown to yellow pigment.
Much of the letter is spent providing evidence to back up the claim that the identified structures are melanosomes, and it will be up to the experts to battle out a consensus. But based on their research, Zhang et al conclude the confirmation of the putative evolutionary precursors of true feathers, and the broach the possibility of decoding the external coloration of the dinosaurs. Indeed, the authors suggest some color schemes in the letter:
"Only phaeomelanosomes have been identified so far in filaments from the tail of Sinosauropteryx, and this suggests that the dark-coloured stripes along the tail in the fossil, and possibly also the filamentous crest along the back, exhibited chestnut to rufous (reddish-brown) tones."
For more details of their research, and more potential dinosaur color schemes, the article is available online:
Image by Chuang Zhao and Lida Xing, courtesy of The Guardian, here.