Analysis reveals tiny dino with rainbow feathers

Caihong juji is a newly described, bird-like dinosaur with an iridescent, rainbow crest. It lived in China about 161 million years ago, and may have used its impressive feathers to attract mates. Illustration by Velizar Simeonovski, The Field Museum, via UT Austin Jackson School of Geosciences.

A team of researchers have conducted a study of the remains of a chicken-sized dinosaur that lived in China about 161 million years ago, during the Jurassic period. Their analysis of the exquisitely-preserved fossil, published January 15, 2018, in the journal Nature Communications, suggests that the small dinosaur had a shaggy ruff of iridescent rainbow feathers.

The scientists think the dinosaur – named Caihong juji, “rainbow with the big crest” in Mandarin — used its flashy neck feathers and a bony crest on its snout to attract mates.

Julia Clarke, a professor in the Department of Geological Sciences at the Univeristy of Texas Jackson School of Geosciences, helped describe the new species. She said in a statement:

Iridescent coloration is well known to be linked to sexual selection and signaling, and we report its earliest evidence in dinosaurs.

The slab of rock containing the dinosaur fossil included a nearly complete skeleton (brown) as well as feather impressions (black). Image via Hu, et al., 2018.

The dinosaur is interesting because it has features that are both ancient and modern, said co-author Xing Xu, a professor 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 – microscopic, wide pigment-containing packages – that may represent the first known occurrence of iridescence similar to that found in many of today’s hummingbirds.

A farmer discovered the slab of rock containing the dinosaur fossil in northern China’s Hebei Province in 2014. The rock contained a nearly complete skeleton surrounded by impressions made by feathers. The impressions preserved the shape of the melanosomes. The researchers 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.

The long and narrow dinosaur skull is similar to a velociraptor’s, a shape that is unique among bird-like dinosaurs. The scale bar is 1 centimeter long. Image via Hu, et al., 2018.

Caihong is also the earliest known dinosaur with asymmetrical feathers, the feather type found on the wingtips of modern birds that helps control flight, said the researchers. But unlike birds today, Caihong’s asymmetrical feathers were on its tail, not its wings — a finding that suggests that early birds may have had a different steering or flight style.

Caihong stands out from the other small, bird-like dinosaurs that lived in China during the Jurassic, the researchers say. While the other dinosaurs had triangular skulls and longer forearm bones than today’s birds, Caihong had a long and narrow skull, and unlike many of these other dinosaurs, its short forelimbs show proportions more like modern birds. Clarke said:

This combination of traits is unusual. 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.

Bottom line: Researchers have described a small dinosaur with rainbow feathers that lived in China about 161 million years ago.

Read more from the University of Texas/Austin

January 26, 2018

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