A groundbreaking research has recognized frequent feather traits amongst flying birds, revealing that every one possess 9 to 11 main feathers, a trait that gives insights into the evolution of flight from dinosaur ancestors. By combining evaluation of museum specimens and fossil knowledge, researchers recommend that flight developed solely as soon as amongst dinosaurs, highlighting the importance of feathers and flight within the evolutionary success of those species. Above is a fossil exhibiting the wing and feathers of the prehistoric chicken Confuciusornis. Credit: Yosef Kiat
Birds can fly— at the very least, most of them can. Flightless birds, reminiscent of penguins and ostriches, have tailored to life with out the necessity for flight. Despite this, there stays a major hole in scientific understanding concerning the variations in wings and feathers between flightless birds and people that may fly.
In a brand new research within the journal PNAS, scientists examined tons of of birds in museum collections and found a collection of feather traits that every one flying birds have in frequent. These “rules” present clues as to how the dinosaur ancestors of contemporary birds first developed the power to fly, and which dinosaurs have been able to flight.
Evolutionary Origins of Bird Flight
Not all dinosaurs developed into birds, however all residing birds are dinosaurs. Birds are members of the group of dinosaurs that survived when an asteroid hit the Earth 66 million years in the past. Long earlier than the asteroid hit, a few of the members of a gaggle of dinosaurs known as Penneraptorans started to evolve feathers and the power to fly.
The wing, highlighting the flight feathers, of Temminck’s Lark. Credit: Yosef Kiat
Members of the Penneraptoran group started to develop feathers earlier than they have been capable of fly; the unique function of feathers might need been for insulation or to draw mates. For occasion, Velocirpator had feathers, but it surely couldn’t fly.
Of course, scientists can’t hop in a time machine to the Cretaceous Period to see whether or not Velociraptors might fly. Instead, paleontologists depend on clues within the animals’ fossilized skeletons, like the dimensions and form of arm/wing bones and wishbones, together with the form of any preserved feathers, to find out which species have been able to true, powered flight. For occasion, the lengthy main feathers alongside the guidelines of birds’ wings are asymmetrical in birds that may fly, however symmetrical in birds that may’t.
Discoveries in Feather Evolution
The quest for clues about dinosaur flight led to a collaboration between Jingmai O’Connor, a paleontologist on the Field Museum in Chicago, and Yosef Kiat, a postdoctoral researcher on the Field.
“Yosef, an ornithologist, was investigating traits like the number of different types of wing feathers in relation to the length of arm bone they attach to, and the degree of asymmetry in birds’ flight feathers,” mentioned O’Connor, the museum’s affiliate curator of fossil reptiles, who focuses on early birds. “Through our collaboration, Yosef is able to track these traits in fossils that are 160-120 million years old, and therefore study the early evolutionary history of feathers.”
The main feathers of a penguin. Credit: Yosef Kiat
Kiat undertook a research of the feathers of each order of residing birds, analyzing specimens from 346 totally different species preserved in museums around the globe. As he regarded on the wings and feathers from hummingbirds and hawks, penguins, and pelicans, he observed a variety of constant traits amongst species that may fly. For occasion, along with asymmetrical feathers, all of the flighted birds had between 9 and 11 main feathers. In flightless birds, the quantity varies extensively— penguins have greater than 40, whereas emus have none. It’s a deceptively easy rule that’s seemingly gone unnoticed by scientists.
Implications for Understanding Dinosaur Flight
“It’s really surprising, that with so many styles of flight we can find in modern birds, they all share this trait of having between 9 and 11 primary feathers,” says Kiat. “And I was surprised that no one seems to have found this before.”
By making use of the details about the variety of main feathers to the general chicken household tree, Kiat and O’Connor additionally discovered that it takes a very long time for birds to evolve a distinct variety of main feathers. “This trait only changes after really long periods of geologic time,” says O’Connor. “It takes a very long time for evolution to act on this trait and change it.”
Blackburnian Warblers within the collections of the Field Museum used on this research. Credit: Yosef Kiat
In addition to fashionable birds, the researchers additionally examined 65 fossil specimens representing 35 totally different species of feathered dinosaurs and extinct birds. By making use of the findings from fashionable birds, the researchers have been capable of extrapolate details about the fossils. “You can basically look at the overlap of the number of primary feathers and the shape of those feathers to determine if a fossil bird could fly, and whether its ancestors could,” says O’Connor.
For occasion, the researchers regarded on the feathered dinosaur Caudipteryx. Caudipteryx had 9 main feathers, however these feathers are almost symmetrical, and the proportions of its wings would have made flight unimaginable. The researchers mentioned it’s doable that Caudipteryx had an ancestor that was able to flight, however that trait was misplaced by the point Caudipteryx arrived on the scene.
Since it takes a very long time for the variety of main feathers to vary, the flightless Caudipteryx retained its 9 primaries. Meanwhile, different feathered fossils’ wings appeared flight-ready— together with these of the earliest recognized chicken, Archaeopteryx, and Microraptor, a tiny, four-winged dinosaur that isn’t a direct ancestor of contemporary birds.
Fossil exhibiting the wings and feathers of the dinosaur Microraptor. Credit: Yosef Kiat
Integrating Knowledge of Evolution
Taken a step additional, these knowledge could inform the dialog amongst scientists in regards to the origins of dinosaurian flight. “It was only recently that scientists realized that birds are not the only flying dinosaurs,” says O’Connor. “And there have been debates about whether flight evolved in dinosaurs just once, or multiple separate times. Our results here seem to suggest that flight only evolved once in dinosaurs, but we have to really recognize that our understanding of flight in dinosaurs is just beginning, and we’re likely still missing some of the earliest stages of feathered wing evolution.”
“Our study, which combines paleontological data based on fossils of extinct species with information from birds that live today, provides interesting insights into feathers and plumage—one of the most interesting evolutionary novelties among vertebrates. Thus, it helps us learn about the evolution of these dinosaurs and highlights the importance of integrating knowledge from different sources for an improved understanding of evolutionary processes,” says Kiat.
“Theropod dinosaurs, including birds, are one of the most successful vertebrate lineages on our planet,” says O’Connor. “One of the reasons that they’re so successful is their flight. One of the other reasons is probably their feathers, because there’s such versatile structures. So any information that can help us understand how these two important features co-evolved that led to this enormous success is really important.”
Reference: “Functional constraints on the number and shape of flight feathers” by Yosef Kiat and Jingmai Okay. O’Connor, 12 February 2024, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2306639121
