New Scientist describes the ground-dwelling carnivore's wing anatomy as similar to a pheasant's.
New Scientist reports that fossils of a flightless, ground-dwelling carnivorous bird with wing anatomy similar to a pheasant's may force a rethink of flight's role in early bird evolution.
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A fossil from southeastern China adds an unexpectedly grounded branch to the early bird family tree. In a Nature study published Oct. 14, researchers describe Yuezhuornis yangyuanensis, a newly named Late Jurassic avialan whose proportions point to a terrestrial, flightless lifestyle.
The specimen comes from the Zhenghe Fauna, a fossil assemblage roughly contemporary with Archaeopteryx. The researchers identify Yuezhuornis as one of the earliest-diverging avialans. Yet its body combined features that do not fit a neat march from dinosaur to modern flier.
The clearest clue is in the limbs. Yuezhuornis had markedly short forelimbs, a proportion common among non-avialan theropod dinosaurs but unusual for an early bird. The study's comparison with 381 living-bird specimens found that its hind-limb proportions most closely resembled terrestrial birds.
New Scientist reports that the fossil is about 148 million to 150 million years old and was discovered in August 2024 in Fujian province. Min Wang of the Chinese Academy of Sciences estimated that the animal stood about half a meter tall and weighed just over 800 grams, roughly the size of a large crow. He suspects it most likely lived in a swampy environment and was probably a good runner.
Its feet supplied another clue about how it lived. A hyperextensible second toe carried a sickle-shaped claw that the researchers interpret as useful for capturing prey. The skull retained closely packed, serrated teeth, while the tail remained long, as in Archaeopteryx. At the same time, features in the hips and lower legs resembled those of later birds.
That mixture matters because powered flight is often treated as the main force that shaped the early bird skeleton. If one of the earliest branches of avialans was already adapted to life on the ground, then early bird evolution may have explored several ecological paths much sooner than the standard flight-first story suggests.
The paper's phylogenetic and morphometric analyses place Yuezhuornis among early avialans while finding strong evidence that it could not fly. The authors argue that its combination of primitive and more derived traits shows early bird anatomy was not assembled through a steady progression toward better flight. Instead, early species appear to have diversified rapidly into different niches.
The fossil does not settle whether the lineage never achieved powered flight or lost it soon after flight evolved. Either scenario complicates the idea that powered flight was the dominant force shaping the early bird body plan. Yuezhuornis is evidence that Jurassic avialans had already diversified into radically different ways of life.
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