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

Reporting by Digi24Read the original at digi24.ro

Executive Summary

A small bird species, *Yuezhuornis yangyuanensis*, was discovered in the Upper Jurassic fossil assemblage known as Fauna Zhenghe in southeastern China, living 150 to 148 million years ago. Analysis of its fossilized skeleton indicated a body weight of approximately 1.8 pounds (0.8 kilograms). The animal exhibited a mosaic of features combining bird and dinosaur traits, including hyperextensible toes resembling 'sickle-shaped' claws, slender skull elements, and a pectoral girdle that shows similarities to primitive birds. These features suggest the animal possessed characteristics consistent with a terrestrial predator adapted for running, similar in limb proportions to modern terrestrial birds like pheasants. Researchers suggest this combination implies that the morphological distinction between birds and dinosaurs may be smaller than previously assumed.
The study positions *Y. yangyuanensis* closer to modern birds in the evolutionary tree than to *Archaeopteryx*, suggesting that flight evolution occurred through multiple, disparate carnivorous dinosaur groups rather than a single linear path. This finding supports the idea that ecological and morphological diversification among avian ancestors was extensive during the origins of avianes, leading to a broader understanding of early bird diversity.

Facts Only

*Yuezhuornis yangyuanensis* was discovered in the Upper Jurassic fossil assemblage Fauna Zhenghe in southeastern China.
The animal lived 150 to 148 million years ago.
Analysis revealed the animal weighed approximately 1.8 pounds (0.8 kilograms).
The species presented a combination of bird and dinosaur features, including hyperextensible toes and 'sickle-shaped' claws similar to deinonychosaurians.
Features like teeth, the pectoral girdle, and the second toe show similarities to dinosaurs, while slender skull bones and pelvis resemble primitive birds.
The limb proportions were most similar to those of terrestrial birds.
Researchers suggest the animal was a small carnivore adapted for running.
The study places *Y. yangyuanensis* closer to modern birds than to *Archaeopteryx*.

Full Take

The discovery of *Y. yangyuanensis* challenges a linear view of avian evolution by demonstrating that morphological divergence occurred through multiple evolutionary pathways among carnivorous dinosaurs, rather than solely through the lineage leading to *Archaeopteryx*. The mosaic nature of its anatomy—combining dinosaurian predatory traits with bird-like skeletal elements—suggests that the defining features separating birds from dinosaurs are more fluid and distributed across a broader spectrum. This implies that the shift toward flight and avian morphology was not a singular event but an extensive process involving numerous ecological niches occupied by proto-birds. The implication for evolutionary biology is that ecological diversity heavily shaped morphological change, as *Y. yangyuanensis* appears to have inhabited an ecological niche distinct from those followed by its relatives, suggesting evolution favored adaptation in various ways rather than strict adherence to a single trajectory toward flight optimization. What are the constraints placed on defining "birdness" when significant morphological overlap exists between groups? How does this understanding of diversified evolutionary paths reshape our perception of evolutionary novelty versus incremental change?

From the original · Digi24

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.

Read the full story at digi24.ro

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