Gorgeous fossil shows ancient bird with super sexy pair of tail feathers

Presentation Yuanchuavis, an extinct bird that lived 120 million years ago in present-day China. Its elaborate tail feathers appear to contain a mix of functional and decorative features, scientists say, revealing new information about the evolution of ancient birds.

Research published today in Current biology describe Yuanchuavis, a Lower Cretaceous bird with a pair of tail feathers longer than its body. Study co-author Jingmai O’Connor of the Field Museum in Chicago says these feathers weren’t very aerodynamic and that they were probably used for ornamental purposes to attract mates.

But this bird was also equipped with a bundle of shorter tail feathers that likely allowed it to fly. For Yuanchuavis, this was a case of sexual selection in tension with natural selection – a combination of pressures that resulted in a remarkably distinctive creature. Paleontologist Wang Min of the Chinese Academy of Sciences is the first author of the article.

There is some really cool science here, but take a moment to marvel at this wonderful fossil. It was mined from the Jehol Lagerstatten, a series of deposits in northeast China “known for extremely well-preserved fossils that sometimes include traces of soft tissue like feathers,” O’Connor explained in an email. . The excellent conservation is the result of rapid burial in ancient lakes, she added. The sediment from which this specimen was extracted dates back 120 million years to the early Cretaceous period, and the name of the extinct animal comes from Yuanchu, a bird in Chinese mythology.

Yuanchuavis was relatively small, about the size of a blue jay. Its skeleton exhibits a combination of primitive and newly derived characteristics, which “speaks to the complexity of early avian evolution and the evolution of the modern bird,” said O’Connor.

The two long tail feathers, 150% of its total body length, are Yuanchuavisthe most distinctive physical trait. Importantly, however, the bird also had a pintail, the combination of the two long strokes and its short, fan-shaped tail. Northern pintails are seen in modern birds such as souimangas and quetzals, but this is the earliest known example of a northern pintail among the Enantiorniths, a group of successful Mesozoic birds.

“The northern pintail is a form of tail that is shaped by both natural and sexual selection, and it serves both purposes: to increase the chances of survival and reproduction,” said O’Connor. “The tail fan provides lift to help during flight while the two elongated tail feathers are adornments that can be used to attract mates. “

As an evolving phenomenon, sexual selection is super interesting because it often goes against a species when it comes to functioning optimally. Birds are particularly prone to it, developing feathers, decorations, vocalizations and elaborate dances. The point is that the demand for an eye-catching and sexy look often leads to the appearance of superfluous, resource-intensive and even detrimental features. But that’s the whole point of these male parades, because they communicate clearly message to curious women: “Despite these wacky characteristics, I am strong, fit, and someone who can help you pass your genes on. This is why evolutionary biologists refer to these sexual manifestations as “honest signals.”

The authors of the new document argue that YuanchuavisHis two elongated tails are exactly that: an honest signal.

“The tail feathers are very long and the long tails are almost always ornamental,” O’Connor explained. “The longer or bigger the feather, the more energy it takes to grow it, so this implies an initial energy investment. Then the feathers create a trail, which makes the flight more difficult, so more energy is needed to move. It cost the bird dear to have the two long feathers, she said, and they were not something that increased his chances of survival. “It means it has to be an ornament,” O’Connor added. “How much of a hindrance this ornament was is hard to say. Its cost may have been offset somewhat by the tail fan.

Suffice it to say that if the male members of Yuanchuavis could fly, they flew very badly.

Michael Pittman, a vertebrate paleontologist at the University of Hong Kong who was not involved in the research, said it is quite possible that sexual selection resulted in elongated feathers, but that “knowledge gaps” still exist in this area. That said, Pittman said the new study “paves the way for a clearer understanding of the early evolution of tail feathers that takes advantage of what we already know about modern birds,” where we can see the tail feathers themselves but we can also directly observe how the tail feathers are used. ”

The idea that sexual selection shaped the tail feathers of Cretaceous birds is not new, Dennis Voeten, a paleontologist at Uppsala University and ancient bird expert, explained in an email.

“It has even been suggested that sexual selection in the small running dinosaurs may have stimulated the development of arm plumage, which would ultimately result in a wing ready to fly,” said Voeten, who was not involved in the research. In other words, sexual selection may have given birth to wings in the first place!

The new study fits well with the emerging idea that the feathers of dinosaurs, including birds, “are highly adaptive,” and it helps explain the “puzzling” diversity of birds throughout evolutionary history. , Voeten said.

Other reasonable assumptions about Yuanchuavis are that, as a bird that did not fly very well, it probably lived in a dense and resource-rich forest, and that the males, weighed down by their long tails, were probably not involved in the rearing of the young.

Additionally, because the Enantiorniths did not survive the Chicxulub mass extinction that wiped out all non-avian dinosaurs, the discovery of Yuanchuavis might help explain why only a few birds survived.

Following: Dinosaur-killing asteroid rewrites bird history.