Birds are the last remaining dinosaurs, and they’re also some of the most vibrantly colored animals on Earth. A new study reveals that these iridescent feathers go way back—like 161 million years back.
Caihong juji, a newly discovered species of dinosaur, was duck-sized with a bony crest on its head, and long, ribbon-like feathers that were likely iridescent. These “rainbow” feathers would have shifted colors and shimmered in the light. Caihong juji means “rainbow with the big crest” in Mandarin.
“When you look at the fossil record, you normally only see hard parts like bone, but every once in a while, soft parts like feathers are preserved, and you get a glimpse into the past,” says Chad Eliason, a postdoctoral researcher at the Field and an author of the study published in Nature Communications.
When scientists examined the feathers under powerful microscopes, they discovered the microscopic color-bearing structures (melanosomes) were still intact. By comparing those structures to structures in the feathers of modern birds, scientists were able to determine what kinds of colors Caihong may have flashed. The best matches? Hummingbirds.
"Hummingbirds have bright, iridescent feathers, but if you took a hummingbird feather and smashed it into tiny pieces, you’d only see black dust. The pigment in the feathers is black, but the shapes of the melanosomes that produce that pigment are what make the colors in hummingbird feathers that we see,” explains Eliason.
Colorful plumage is used in modern birds to attract mates. The rainbow feathers of Caihong might be a prehistoric version of a peacock’s iridescent tail. Caihong is the oldest known example of platelet-shaped melanosomes typically found in bright iridescent feathers. It’s also the earliest known animal with asymmetrical feathers.
But while Caihong’s feathers were a first, it had other traits associated with much earlier species of dinosaurs, including the bony crest on its head. “It has a velociraptor-type skull on the body of this very avian, fully feathered, fluffy kind of form,” says co-author Julia Clarke of the University of Texas at Austin.
This combination of old and new traits, says Eliason, is evidence of mosaic evolution, the concept of different traits evolving independently from each other. “This discovery gives us insight into the tempo of how fast these features were evolving,” he adds.
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Quanguo Li of the China University of Geosciences in Beijing and Matthew D. Shawkey of the University of Ghent in Belgium also worked on the study. The research was funded by the U.S. National Science Foundation and the National Science Foundation of China.