A newly discovered species of bird-like dinosaur, Caihong juji, had a beautiful iridescent coloration, according to a study published in the journal Nature Communications.
Caihong juji lived in China about 161 million years ago and may have used its impressive feathers to attract mates. Image credit: Velizar Simeonovski, Field Museum.
Caihong juji is part of a group of small, bird-like dinosaurs that lived in what is now China during the Jurassic period.
This dinosaur was tiny, about the size of a duck, with a bony crest on its head and long, ribbon-like feathers. And, based on analysis of its fossilized feathers, the feathers on its head, wings, and tail were iridescent, with colors that shimmered and shifted in the light.
“Iridescent coloration is well known to be linked to sexual selection and signaling, and we report its earliest evidence in dinosaurs. Caihong juji may have a cute nickname in English, Rainbow, but it has serious scientific implications,” said co-lead author Professor Julia Clarke, from the University of Texas at Austin.
“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,” said co-author Dr. Chad Eliason, a postdoctoral researcher at the Field Museum.
The slab of rock from China’s Hebei Province where Caihong juji was discovered by a farmer in 2014 contained a nearly complete skeleton surrounded by impressions made by feathers.
The impressions preserved the shape of the melanosomes. The paleontologists compared the melanosome impressions to melanosomes found in living birds and found that they most closely resembled those in the iridescent, rainbow feathers of hummingbirds.
“Aside from making Jurassic ecosystems of 161 million years ago more colorful, Caihong juji is interesting because it has features that are both ancient and modern,” said co-lead author Professor Xing Xu, from the Institute of Vertebrate Paleontology and Paleoanthropology at the Chinese Academy of Sciences.
“The bony crest is a feature usually seen in dinosaurs from earlier eras, while its neck feathers show evidence of melanosomes that may represent the first known occurrence of iridescence similar to that found in a variety of hummingbird species living today.”
“There are crests associated with sexual selection previously known only in earlier dinosaurs, and yet there is also a bird mechanism of signaling or display appearing for the first time,” Professor Clarke added.
Caihong juji is also the earliest known animal with asymmetrical feathers — a feature used by modern birds to steer when flying. This dinosaur couldn’t fly, though — its feathers were probably primarily used to attract mates and keep warm.
While modern birds’ asymmetrical feathers are on their wingtips, Caihong juji’s were on its tail.
“The tail feathers are asymmetrical but wing feathers not, a bizarre feature previously unknown among dinosaurs including birds,” Professor Xu said.
“This suggests that controlling flight might have been first evolved with tail feathers during some kind of aerial locomotion.”
“Caihong juji stands out even among its closest relatives,” Professor Xu added.
“While the other dinosaurs have bird-like, triangular skulls and long forearm bones in comparison to birds today, this dinosaur had a long and narrow skull, and unlike many of these other dinosaurs, its short forelimbs show proportions more akin to modern birds.”
“This combination of traits is unusual,” Professor Clarke.
“It has a rather Velociraptor-looking low and long skull with this fully feathered, shaggy kind of plumage and a big fan tail. It is really cool… or maybe creepy looking depending on your perspective.”
_____
Dongyu Hu et al. 2018. A bony-crested Jurassic dinosaur with evidence of iridescent plumage highlights complexity in early paravian evolution. Nature Communications 9, article number: 217; doi: 10.1038/s41467-017-02515-y
