'Rainbow dinosaur' had iridescent feathers like a hummingbird

Scientists say they've discovered a new dinosaur that boasted iridescent feathers, particularly on its head, neck and chest, with colours that shimmered and shifted in the light, like those of hummingbirds.

Microscopic structures in feathers provide evidence of Caihong's shimmery colours

Caihong was a crow-sized, bird-like dinosaur with colourful feathers from northeastern China that lived 161 million years ago during the Jurassic Period. (Velizar Simeonovski/The Field Museum)

There's not a pot of gold at the end of the rainbow. There's an iridescent dinosaur.

Scientists on Monday announced the discovery of a crow-sized, bird-like dinosaur with colourful feathers from northeastern China that lived 161 million years ago during the Jurassic Period.

They named it Caihong, the Mandarin word for rainbow. Microscopic structures in the exquisitely preserved, nearly complete fossil unearthed in Hebei Province indicated that it boasted iridescent feathers, particularly on its head, neck and chest, with colours that shimmered and shifted in the light, like those of hummingbirds.

The exquisitely preserved, nearly complete fossil was unearthed in Hebei Province in northeastern China. (Yu et al./Nature Communications)

The discovery "suggests a more colourful Jurassic World than we previously imagined," said evolutionary biologist Chad Eliason of the Field Museum in Chicago, one of the researchers in the study published in the journal Nature Communications.

Using powerful microscopes, the scientists detected within the feathers the remnants of organelles called melanosomes 
responsible for pigmentation. Their shape determines the colour. 

Caihong's feathers had pancake-shaped melanosomes similar to those of hummingbirds with iridescent feathers.

Not for flying

Much of its body had dark feathers, but ribbon-like iridescent feathers covered its head and neck. While it possessed many bird-like characteristics, the researchers doubted it could actually get airborne. Its plumage could have attracted mates while also providing insulation.

Hummingbirds with iridescent feathers have pancake-shaped organelles in their feathers called melanosomes. The shape of the melanosomes determines their colour. (Heather Skeen/The Field Museum)

Caihong was a two-legged predator with a Velociraptor-like skull and sharp teeth, probably hunting small mammals and lizards. It had crests above its eyes that looked like bony eyebrows.

Many dinosaurs possessed feathers. Birds evolved from small feathered dinosaurs near the end of the Jurassic Period. Caihong had fuzzy feathers and pennaceous ones, those that look like writing quills. It is the earliest-known creature with asymmetrical feathers, a trait used by birds to steer when flying. Caihong's were on its tail, suggesting tail feathers, not arm feathers, were first utilized for aerodynamic locomotion.

"It is extremely similar to some early birds such as Archaeopteryx," said paleontologist Xing Xu of the Chinese Academy of Sciences, referring to the earliest-known bird, which lived 150 million years ago. "Its forelimbs were configured like wings. To be honest, I am not sure what function the feathers have, and I don't think that you can completely exclude the possibility that the feathers helped the animal to get in the air."

Fossilized nanostructures from Caihong feathers can be seen in its neck feathers, a, b, and d, and a back feather, c. They're compared to structures seen in the feathers of Anna’s hummingbird (Calypte anna), e; white-tailed starfrontlet (Coeligena phalerata), f; black-tailed trainbearer (Lesbia victoriae), g and moustached treeswift (Hemiprocne mystacea), h. (Yu et al./Nature Communications)

Asked what someone might say upon seeing Caihong, University of Texas paleontologist Julia Clarke said, "'Wow!' And if they are anything like me, they might want one as a pet. Not suitable for children."

The dinosaur's full scientific name, Caihong juji, means "rainbow with a big crest." 

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