Flightless Jurassic bird was like a carnivorous pheasant with killer claws

Paleontologists in China have discovered a small Jurassic bird that was likely a land-based predator, resembling a carnivorous pheasant with lethal claws. The fossilized remains, named Yuezhuornis yangyuanensis, were unearthed in the Upper Jurassic Zhenghe Fauna in southeastern China. This creature, which lived 150 million to 148 million years ago, had characteristics of both birds and dinosaurs, indicating that the earliest birds exhibited a wider range of lifestyles than previously believed.

Y. yangyuanensis weighed approximately 1.8 pounds (0.8 kilograms) and measured up to the size of a crow. It possessed hyperextensible toes, akin to those of predatory dinosaurs like Velociraptor, as well as shorter forelimbs compared to its hind limbs. These peculiar traits are uncommon in modern birds and other Jurassic paravians, which typically have extended forelimbs to generate lift for takeoff.

However, Y. yangyuanensis also exhibited a slender skull, sparsely spaced teeth, and a pelvis resembling that of early birds, suggesting a diet primarily consisting of meat.

The researchers observed that Y. yangyuanensis shared the most similar limb proportions with terrestrial birds among the 377 living bird species analyzed. The paleontologists concluded that this flightless bird was a small carnivore, akin to a pheasant, well-adapted for running rather than tree-dwelling or swamp life. The mosaic of features suggests that Y. yangyuanensis occupied an ecological niche rarely exploited by early birds, and that the evolution of flight may not have followed a systematic progression among carnivorous dinosaurs closely related to birds.