Chinese bird fossil: mix of old and new.

Chinese bird fossil: Mix of old and new

Documenting an important step in the evolution of avian flight, paleontologists have indentified the 135-million-year-old fossil remains of a bird from northeast China. The sparrow-sized specimen is the earliest known example of a bird with modernized flying ability, reports Paul C. Sereno of the University of Chicago, who announced the find last week at the annual meeting of the Society of Vertebrate Paleontology, held in Lawrence, Kan.

The still-unnamed Chinese bird is about 10 million to 15 million years younger than the oldest known bird, Archeopteryx, and displays several flight features that the cros-sized Archeopteryx lacked. "This is the first bird with the capacity for a modern flight stroke," says Sereno. He studied the new specimen with Chenggang Rao of the Beijing (China) Natural History Museum.

The fossil shows an intriguing mix of modern avian features and primitive characteristics retained from reptilian ancestors. The bird had flight-specialized shoulders and a distinctly avian adaption called the pygostyle -- a shortened set of tail vertebrae fused into one bone. The shorter tail allowed the bird's mass to center ove the shoulders, aiding in flight. Archeopteryx and the dinosaurs from which it presumably descended had longer tails that balanced weight over the hind feet -- a trait more useful for running alont the ground. Many paleontologists believe Archeopteryx could not fly well, and they envision the creature flapping its wings while jumping after insects.

The Chinese specimen, however, displays adaptations for free life. The claws of its feet were long and curved, allowing the bird to perch on a branch better than Archeopteryx, says Sereno. The "hand" bones in the wings had a shrunken first digit and an enlarged second digit, an arrangement resembling that seen in modern birds.

The fossil also shows many characteristics lacking in modern birds, such as stomach ribs, unfused hand bones and a primitive pubic bone.

A 10-year-old boy discovered the specimen in the rocky remains of an ancient lake that existed during the early Cretaceous period. The Chinese bird joins several slightly younger fossils found in Spain (SN: 2/13/88, p.102) as the only known birds from this crucial phase in avian history. Some of its primitive features, including stomach ribs, do not appear in the Spanish fossils.

Larry D. Martin, a paleontologist at the University of Kansas in Lawrence, says the great geographic distance between the Chinese and Spanish fossils indicates that modernized flying ability must have developed and spread across the continents long before the time of these birds.