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Rainbow Dinosaur With Colourful Hummingbird Feathers

S u m m a r y :
Fossils of a rainbow dinosaur with colourful hummingbird feathers have been discovered in China. The findings are published in the journal Nature Communications.

Meet Caihong juji, Rainbow-Feathered Dino

The remains of a hitherto-unknown dinosaur have been discovered in northeastern China by a farmer; the creature is thought to have lived some 161 million years ago. Its fossilised feathers were so well-preserved that the researchers, led by Dr Dongyu Hu from Shenyang Normal University, were able to observe the colour-bearing structures under the microscope: by carefully examining these in details, the team concluded that the dinosaur had iridescent rainbow feathers much like those of the hummingbird.

This phenomenal trait has given its name, Caihong juji, phrase meaning ‘rainbow with the big crest’ in Mandarin.

A hummingbird. Photo Credits: Heather Skeen.

The researchers point out that the preservation of the fossils is exceptional, given the details they have extracted from its analysis.

“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 study author Chad Eliason.

What was Caihong juji like?

Reconstructing the dinosaur from the fossils available showed that C. juji was as tiny as a duck, bearing a bony crest on its head, and ribbon-like feathers. Upon analysing the latter, Hu and his colleagues concluded that the feathers the dinosaur wore on its head, wings, and tail were most likely to have been iridescent, with shimmering colours.

Holotype fossil of rainbow dinosaur, Caihong juji. Photo Credits: Yu et al., 2018.

The team was able to lay their eyes on the imprints left behind by the melanosomes, the cell organelles that carry the colour pigment. While the pigment itself had disappeared, the physical structure of the melanosomes were still there to help the scientists determine the colour of the feathers. The researchers explain that the pigment is not needed to work out the colour, but the very constitution of the melanosomes itself is enough: the different shapes of these organelles are known to reflect different colours of light.

“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.

So, Eliason and his colleagues figured out the colour of C. juji by comparing the shapes its melanosomes with those of the hummingbird’s: it turns out that they are very similar.

The hummingbird dinosaur, named Caihong juji. Image Credits: Velizar Simeonovski.

What Makes You Different Makes You Beautiful

C. juji had more than one special, different trait. For instance, it appears to be the oldest known animal with asymmetrical feathers; this same feature is seen among modern birds, acting as a steering aid during flying. However, C. juji could not fly; the researchers believe its coloured feathers were meant to attract mates, and to keep them warm.

Another unusual feature is that, unlike modern birds whose asymmetrical feathers are on their wingtips, C. juji’s were on its tail.

“The tail feathers are asymmetrical but wing feathers not, a bizarre feature previously unknown among dinosaurs including birds,” said co-author Xing Xu. “This suggests that controlling [flight] might have been first evolved with tail feathers during some kind of aerial locomotion.”

A Velociraptor Hummingbird

Another astonishing finding is its combination of traits. Well, it’s a dinosaur with rainbow feathers, and a bony crest on the head!

“This combination of traits is rather unusual,” says co-author Julia Clarke of the University of Texas at Austin. “It has a velociraptor-type skull on the body of this very avian, fully feathered, fluffy kind of form.”


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