Paleontologists discovered a bird from the Jurassic period that resembled a carnivorous pheasant and had deadly claws. Why couldn't it fly?

A primitive bird, discovered in China, had an unusual mixture of bird and dinosaur features, and its anatomy suggests that it was a terrestrial predator, adapted for running and equipped with strong claws, notes Live Science. The discovery shows that the first birds had a greater diversity of forms and ways of life than previously thought. Paleontologists in China discovered a small bird from the Jurassic period, which was probably a terrestrial predator—resembling a carnivorous pheasant with deadly claws. It had some bird features and others of dinosaurs, which suggests that the first birds had a greater diversity of ways of life than previously thought. Birds in the Jurassic first appeared 150 to 148 million years ago, and their fossils are rare, so experts are just beginning to understand how early birds diversified and how they developed the ability to fly. Researchers discovered the recently identified species, Yuezhuornis yangyuanensis, in 2024, in the fossil assemblage known as Fauna Zhenghe from the Upper Jurassic, in southeastern China. It lived 150 to 148 million years ago, approximately during the period when birds began to appear in the fossil record. The team published the discoveries on Wednesday (October 14) in the journal Nature. Analysis of the fossilized skeleton revealed that the animal was small and weighed approximately 1.8 pounds (0.8 kilograms). "It was probably the size of a chick," said Min Wang, a researcher at the Chinese Academy of Sciences, to Live Science via email. A mixture of bird and dinosaur features Y. yangyuanensis presented a combination of features specific to birds and predatory dinosaurs of the Deinonychosauria order, such as Velociraptor, known for sickle-shaped toes. It had hyperextensible toes, similar to those of deinonychosaurians, and its forelimbs were about one-third shorter than its hindlimbs. This is strange, as modern birds and many other theropods from the Jurassic period—the group that includes bird-like dinosaurs, including bird ancestors, and modern birds themselves—have long forelimbs, intended to provide greater lifting force for flight. Y. yangyuanensis also had slender skull elements and sparsely spaced teeth. These features, along with the curved toes, resembling claws, capable of catching prey, suggest that the animal's diet included meat. Read also: Dinosaurs would have built their own "incubators" for eggs. How they survived in cold regions "Its key anatomical features represent a combination of dinosaur and bird traits: for example, the teeth, the pectoral girdle, and especially the second toe, which is hyperextensible and has a 'sickle-shaped' 'claw', are similar to those of dinosaurs," said Wang. At the same time, he mentioned that the slender skull bones and pelvis similar to those of birds are comparable to those of primitive birds. This combination of features suggests that "the morphological difference between birds and dinosaurs is much smaller than we thought," he added. A terrestrial bird, adapted for running Comparisons with 377 species of modern birds have shown that the proportions of the limbs of the Y. yangyuanensis species were most similar to those of terrestrial birds. Wang suggested that Y. yangyuanensis was a bird that could not fly, but was not specialized to live in trees or roam the swamps of the region. It was a small carnivore, with proportions similar to a pheasant, well adapted for running. "I think there are no modern birds directly comparable," he said. The mosaic of features suggests that Y. yangyuanensis may have occupied an ecological niche rarely used by primitive birds and that there was no systematic evolution towards optimizing flight, Wang asserted. Read also: Tyrannosaurus rex, a dinosaur with warm blood: discovery made with the help of a tooth. The reptile could live in icy regions A different evolutionary path than other primitive birds Despite not being able to fly, Wang and his colleagues place Y. yangyuanensis closer, in the evolutionary tree, to modern birds than to Archaeopteryx, one of the earliest proto-birds in the world, which lived about 150 million years ago and is believed to have been capable of flight. This comes to complete the evidence according to which "the ability to fly did not appear at once, but several times among disparate groups of carnivorous dinosaurs closely related to birds," wrote Fernando Novas, a paleontologist at the Felix de Azara Natural History Foundation in Buenos Aires, Argentina, who did not participate in the study, in an accompanying article published in the journal Nature. This includes the evolution of flight in primitive birds and theropod dinosaurs, which had membranous folds similar to wing membranes, as well as in the microraptorids with four wings. Y. yangyuanensis seems to have followed a different path, avoiding the flight mode of its relatives. "This highlights the extraordinary breadth of ecological and morphological diversification that occurred around the origins of avianes," said Wang. Editor: Ana Petrescu