for National Geographic News
Paleontologists in China have unearthed a 121-million-year-old fossil bird embryo that is likely the world's oldest. (See pictures.) The bird was found scrunched in an oval-shaped space slightly smaller than a chicken eggone of several clues that suggest the bird never hatched.
More important, scientists say, is the evidence that the embryonic bird had feathers, a large skull, and hardened bones. The findings support the notion that early birds, like dinosaurs, were well developed at birth and able to move and forage on their own from the get-go.
The same theory suggests that birds that give birth to helpless, naked young evolved much later.
Paleontologists Zhou Zhonghe and Zhang Fucheng discovered the fossil in Liaoning Province in northeastern China. Employees of the Institute of Vertebrate Paleo-anthropology at Beijing's Chinese Academy of Sciences, the researchers describe their find in tomorrow's issue of the journal Science.
The bird is preserved in a space that measures approximately 1.4 by 0.8 inches (35 by 20 millimeters), which is bigger than a robin's egg. No eggshell was preserved.
"We did think about the possibility of the fossil not in an egg. However, several lines of evidence appear to exclude this," Zhou said.
The fossil's egglike shape provides one bit of evidence. Another is that the fossilized bird rests in a "tucked" posture that is consistent with a late-stage embryo rather than a hatchling, the researchers said. They also note that the bird's feathers did not differentiate into barbs (the side structures of a feather that branch from the shaft), which is typical of a late embryo and not a hatchling.
"It is admittedly still a mystery why no eggshell was preserved," Zhou said.
Kevin Padian is a professor in the department of integrative biology and curator of the Museum of Paleontology at the University of California, Berkeley. He agrees that the fossil is likely that of a bird embryo and not a recent hatchling.
Zhou believes the bird is an enantiornithine, the most common bird type found during the early Cretaceous period in China. The Cretaceous period spanned from bout 145 million to 65 million years ago.
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