“Feathered dragon” had some of the longest tail feathers ever found on a fossil bird

Birds have all kinds of fancy decorations for attracting mates— male peacocks have a fan of feathers accented with shimmering blue eye-spots, birds of paradise do courtship dances that highlight their fluffy plumes, and female mallard ducks pick males with shiny green heads and bright yellow bills. A new fossil discovery shows that birds’ over-the-top ornamentation dates back to the time of the dinosaurs. In a new study published in the journal PLOS One, researchers described a new species of fossil bird, whose name means “feathered dragon,” with tail feathers twice as long as its body.

“Plumadraco was the size of an American robin, but its tail feathers were about a foot long, twice the length of its body,” says Alex Clark, a PhD candidate at the Field Museum and the University of Chicago and lead author of the paper. “They’re some of the proportionally longest tail feathers ever found in a fossil bird.”

Birds are the only members of the dinosaur family that didn’t die out from the effects of an asteroid hitting the Earth 66 million years ago. (That means that every bird you’ve ever heard of, including sparrows, pigeons, and Plumadraco, are all dinosaurs.) But only one group of dinosaur-birds survived the asteroid strike. The most diverse group of birds alive at the time, the enantiornithines, all died out alongside the non-bird dinosaurs. Plumadraco lived about 121 million years ago during the Cretaceous Period, well before the big extinction event, but it was part of the enantiornithine group of birds.

Clark came across the fossil on a research trip to China’s Shandong Tianyu Museum with his advisor and co-author, Field Museum curator Jingmai O’Connor. As he perused hundreds of fossil birds, one in particular caught his eye.

“I saw this little guy, and I did a double-take when I saw the tail feathers,” says Clark. “I’m really interested in the way birds do displays to attract mates, and I thought that these tail feathers were so crazy, they had to be used for something like that.”

Clark and his colleagues analyzed the fossil, comparing it to other enantiornithine birds, and determined that it was a new species to science. Clark named it Plumadraco bankoorum— “Banko’s feathered dragon,” in honor of the father and son team Winston and Paul Banko, who have dedicated decades to studying and protecting living birds.

Clark’s examination of Plumadraco has yielded several hypotheses about what this ancient bird was like in life.

It’s hard to tell the sex of a fossil animal, since the soft tissues of sex organs are rarely preserved. However, the length of Plumadraco’s tail feathers indicate that the specimens identified in this study were probably males. “There are many examples of both male and female modern birds with long, showy feathers, but there seems to be this certain threshold where, if feathers reach a certain proportional length, then it tends to be a trait that males have developed in order to attract females,” says Clark. “Plus, the fossils of some other enantiornithine birds show remnants of muscle tissue along the tail region, and based on those muscles, birds like Plumadraco would have had pretty limited movement for their tails. However, they could pump their tail feathers up and down, and that’s a behavior that we see across birds today that do courtship displays only in males.”

The stiff spines at the center of Plumadraco’s tail feathers, and the tapered shape ending with a rounded tip, suggest that males would raise their tail feathers, and the ends of those feathers would move back and forth in a sort of “flickering” motion.

The team also learned about the color of Plumadraco’s tail feathers. Using a handheld mass spectrometer, a chemical instrument that looks a little like a ray gun, they analyzed the chemical makeup of the fossil. Based on the concentrations of different chemicals present, Plumadraco’s feathers were probably dark brown, or black. It’s possible that there was some sort of eye-catching color at the tips of its tail feathers— maybe something iridescent or blue, since those colors are produced by the structure of the cells rather than by the pigments whose chemical signatures were measured in this study.

These insights into Plumadraco’s physiology and behavior help scientists better understand birds today.

“This fossil, maybe more than any other fossil bird that’s ever been discovered, shows that birds have been evolving costly, elongate, specialized features to attract mates for a long, long time,” says Clark. “Based on these fossils, female choice in selecting ornamented males has been playing a huge part in how birds look and behave for more than 120 million years.”