The discovery of a 6-inch (15 cm) fossil of a small bird, 150 million years old, reveals unexpected modern anatomical features. This fossil, named
Baminornis zhenghensis, challenges our understanding of the origin and diversification of birds.
Until now,
Archaeopteryx, discovered in Germany in 1861, was considered the only undisputed bird from the Jurassic period. However,
Baminornis exhibits characteristics much closer to modern birds, including a short tail and a bone structure adapted for more efficient flight. This discovery suggests that bird evolution was already well advanced at that time.
Baminornis zhenghensis.
Image Chuang Zhao. A bird with modern traits
Baminornis zhenghensis possesses a pygostyle, a bone formed by the fusion of caudal vertebrae, characteristic of modern birds. This anatomical innovation, absent in
Archaeopteryx, improves aerodynamics by stabilizing the tail during flight. Additionally, its pelvic and scapular girdles resemble those of modern birds, although its clawed hands still recall those of theropod dinosaurs.
The coexistence of primitive and evolved traits in
Baminornis illustrates a phenomenon of mosaic evolution. This unique combination shows that different parts of the body evolved at varying rates, blurring the boundary between dinosaurs and birds. Researchers emphasize that this mosaic evolution complicates the classification of early birds.
Finally, the discovery of
Baminornis pushes back the appearance of short-tailed birds by nearly 20 million years. Until now, the oldest known specimens dated back to the Cretaceous period. This advance suggests that modern birds began diversifying much earlier than expected, opening new perspectives on their evolutionary history.
Early diversification of birds
The discovery of
Baminornis in China, over 5,470 miles (8,800 km) from the German site of
Archaeopteryx, indicates that birds were already widely distributed during the Jurassic period. This geographical distribution suggests a much older diversification than previously thought, possibly dating back to 172-164 million years ago. Researchers estimate that several bird lineages already coexisted at that time.
Researchers also found a furcula (wishbone) belonging to another bird, more evolved than
Archaeopteryx. Although too fragmentary to be named, this fossil could belong to a group of modern birds (Ornithuromorpha) previously only known from the Cretaceous period. This discovery reinforces the idea of an early diversification of birds.
Finally,
Baminornis lived in a swampy environment, alongside dinosaurs like Fujianvenator, turtles, and semi-aquatic reptiles. This complex ecosystem shows that early birds already occupied varied ecological niches, long before the appearance of modern birds.
To go further: How did birds evolve from dinosaurs?
Birds descended from small feathered theropod dinosaurs, a group that includes famous predators like
Velociraptor. This transition occurred over tens of millions of years, with the gradual appearance of avian traits, such as feathers, wings, and hollow bones. Fossils like
Baminornis and
Archaeopteryx show a combination of primitive (clawed hands, teeth) and modern (pygostyle, asymmetrical feathers) characteristics, illustrating mosaic evolution.
Feathers, initially developed for thermal insulation or courtship displays, were later co-opted for flight. Wings, resulting from modifications of the forelimbs, allowed early birds to glide, then actively fly. This adaptation was favored by anatomical changes, such as the reduction of the tail and the development of the pygostyle, which improve aerodynamics.
Finally, the discovery of
Baminornis in China and
Archaeopteryx in Germany shows that early birds were already diversified and widespread during the Jurassic period. This early diversification suggests that bird evolution began well before this period, likely around 170 million years ago. Current research continues to reveal key fossils, refining our understanding of this major evolutionary transition.
Article author: Cédric DEPOND