Figure 2.

Comparison of melanosome shape (in extant bird feathers) for different colour categories. Box plots of mean width (a), length (b), and aspect ratio (c) of measured melanosomes from 232 birds of various feather types, based on the dataset of Li et al. [11] with non-iridescent structural colour added as a new colour category. SEM images of melanosomes from six colour categories in feathers of the extant taxa: (d) black feathers of wrinkled hornbill (Rhabdotorrhinus corrugatus), (e) brown feathers of the great jacamar (Jacamerops aureus), (f) grey feather of the toucan barbet (Semnornis ramphastinus), (g) iridescent feather of the great jacamar (Jacamerops aureus), (h) feathers expressing non-iridescent structural colour of the blue paradise flycatcher (Terpsiphone cyanescens), and (i) black feather of an African penguin (Spheniscus demersus). (Online version in colour.)