Paleontologists examined fossils 160 million years old Anchiornis huxleya type of non-avian theropod dinosaur from the Late Jurassic Tiaojishan Formation in northeastern China, retained its feathers and found that these dinosaurs lost the ability to fly. This is an extremely rare discovery that provides a glimpse into the work of creatures that lived 160 million years ago, and their influence on the evolution of flight in dinosaurs and birds.
This fossil Anchiornis huxley It displays almost complete wings and maintains feather colour, allowing detailed identification of wing shape. Image credit: Kyat et alMon: 10.1038/s42003-025-09019-2.
Tel Aviv University paleontologist Yosef Kayat and his colleagues said: “This discovery is of broad importance, because it indicates that the evolution of flight during the evolution of dinosaurs and birds was much more complex than previously thought.”
“In fact, some species may have developed basic flight capabilities, only to lose them later in their evolution.”
“The dinosaur lineage separated from other reptiles 240 million years ago.”
“Shortly thereafter (on an evolutionary time scale) many dinosaurs evolved feathers – a unique, lightweight, strong organic structure made of protein and used primarily for flight and to maintain body temperature.”
About 175 million years ago, a lineage of feathered dinosaurs appeared Pinaraptura Back – the distant ancestors of modern birds and the only lineage of dinosaurs to survive the mass extinction that marked the end of the Mesozoic Era 66 million years ago.
As far as we know, the Benaraptora group evolved feathers for flight, but it’s possible that when environmental conditions changed, some of these dinosaurs lost their ability to fly — just like ostriches and penguins do today.
In this study, researchers examined nine specimens from a species of feathered penaraptoran dinosaur called Anchiornis huxley.
Among the rare fossil finds, these fossils – and several hundred similar fossils – have been preserved with their feathers intact, thanks to the special conditions that prevailed in the area during fossilization.
Specifically, the nine fossils examined in the study were chosen because they retained the color of their wing feathers — white with a black spot at the tip.
“Feathers grow for two to three weeks,” Dr. Kiat said.
“When they reach their final size, they separate from the blood vessels that nourished them during growth and become dead matter.”
“Over time, they are shed and replaced with new feathers – in a process called molting, which tells an important story: birds that depend on flight, and therefore on the feathers that enable them to fly, molt in an orderly and gradual way that maintains the symmetry of the wings and allows them to continue flying during the molting process.”
“On the other hand, in birds that do not have the ability to fly, molting is more random and irregular.”
“Thus, the molting pattern tells us whether a particular winged creature is capable of flight.”
The coloring of feathers preserved in dinosaur fossils from China allowed researchers to identify the structure of the wing, where the tip is marked by a continuous line of black spots.
Moreover, they were able to distinguish new feathers that had not yet fully developed, as their black spots deviated from the black line.
Close examination of the new feathers in the nine fossils revealed that molting did not occur in an organized manner.
“Based on my knowledge of modern birds, I have identified a pattern of moulting that suggests these dinosaurs may have been flightless,” Dr. Kiat said.
“This is a particularly rare and exciting discovery: the coloration of preserved feathers has given us a unique opportunity to learn about the functional characteristic of these ancient creatures – not just the body structure preserved in fossil skeletons and bones.”
He added: “Feather molt seems like a small technical detail, but when examined in fossils, it could change everything we thought about the origins of flight.”
“Anchiornis huxley It now joins the list of dinosaurs that were feathered but unable to fly, highlighting how complex and diverse the evolution of wings really was.
the Results It was published in the magazine Communication biology.
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Y. advice et al. 2025. Wing Morphology Anchiornis huxley and the evolution of molting strategies in paraavian dinosaurs. Commune Byul 8, 1633; Two: 10.1038/s42003-025-09019-2