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The fossil was discovered in Jehol Biota – an ecosystem dating back 133 to 120 million years – in northeast China, and the deposits it contains have been a treasure trove of fossil finds, including examples of old theft. The researchers nicknamed the species Yuanchuavis after Yuanchu, a Chinese mythological bird.
“We’ve never seen this combination of different types of tail feathers before in a fossil bird,” Jingmai O’Connor, study author and paleontologist at the Field Museum in Chicago, said in a statement. O’Connor is the Associate Curator of Fossil Reptiles at the Negaunee Integrative Research Center at the Field Museum.
“He had a fan of short feathers at the base, then two extremely long feathers,” O’Connor said. “The long feathers were dominated by the central spine, called the rachis, then variegated at the end. The combination of a short-tailed fan with two long feathers is called a pintail, it is seen in some modern birds like the souimangas and quetzals. “
Yuanchuavis likely flew the same way as a quetzal, a forest bird that lacks the most exceptional flight abilities, O’Connor said. The pintail’s feathers were large enough to create a significant drag, despite being light.
Short tails are associated with birds that live in harsh environments, where they depend on their ability to fly as a survival skill, like seabirds. More elaborate tails are often found on birds living in forests.
“This new finding vividly demonstrates how the interplay between natural and sexual selections has shaped the tails of birds since their earliest history,” said Wang Min, study author and researcher at the Chinese Academy of sciences, in a press release. “Yuanchuavis is the first documented occurrence of a pintail in Enantiornithes, the most successful Mesozoic group of birds.”
Scientists recognized two different tail structures from other combined enantiornithins in Yuanchuavis.
“The tail fan is aerodynamically functional, while elongated central paired plumes are used for display, which together reflect the interplay between natural and sexual selection,” Wang said.
Animals adapt not only to survive, but also to help their particular species persist. In this case, Yuanchuavis developed tail feathers which hampered his flight abilities and made him more visible to predators. The discovery highlights how important sexual selection is during evolution, O’Connor said.
“Scientists call a trait like a fancy big tail an ‘honest signal’ because it is damaging, so if an animal with it is able to survive with this handicap it is a sign that it is really in good shape,” O’Connor said. “A female bird would look at a male with awkward, bulky tail feathers and think, ‘Dang, if he’s able to survive even with such a ridiculous tail, he must have some really good genes.'”
The birds with elaborate feathers tend to be males. They are so focused on caring for their feathers that they are not particularly good at caring for their offspring. The flashy feathers would also attract predators to the nests. But the simpler females stay with their chicks and take care of them.
Despite the fact that enantiornithins initially flourished, they did not survive the extinction event that wiped out dinosaurs 66 million years ago. This is probably due to the fact that they lived in forests, which burned down after the asteroid impact, or because they had not adapted to rapid growth.
“Understanding why living birds are the most successful group of vertebrates on earth today is an extremely important evolutionary matter, because anything that has made them so successful has probably also allowed them to survive a giant meteor hitting the planet when all other birds and dinosaurs have gone extinct, ”O’Connor said.
Fossils don’t always reveal how sexual selection shapes a species.
“The well-preserved tail feathers of this new fossil bird provide excellent information on how sexual selection has shaped the avian tail from its earliest stage,” Wang said.
“The complexity we see in Yuanchuavis’s feathers is related to one of the reasons we hypothesize that living birds are so incredibly diverse, as they can separate into different species simply by differences in plumage. and vocals differences, ”O’Connor said. “It’s unbelievable that Yuanchuavis lets us assume that this kind of plumage complexity may have already been present in the early Cretaceous.”
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