Iridescent structural coloration in a crested Cretaceous enantiornithine bird from Jehol Biota

A combination of sectioning and microscopy techniques, along with the application of finite-difference-time-domain modeling on a fossil feather, novelly results in the estimation of the range of iridescent colors from fossilized melanosomes preserved in the elongate head crest feathers of a new Cretaceous enantiornithine bird. The densely packed rod-like melanosomes yield are estimated to have yielded from red to deep blue iridescent coloration of the head feathers. The shape and density of these melanosome may have also further increased the feather’s structural strength. This occurrence on a likely male individual is highly suggestive of both a signaling function of the iridescent crest, and a potential behavioral role in adjusting the angle of light incidence to control the display of this iridescent structural coloration.