Study: adolescent pregnancy found in dinosaurs

BEIJING, Jan. 15 (Xinhuanet) -- Researchers have discovered medullary bone, a type of tissue present in modern birds when they are developing eggs, in three dinosaur fossils, indicating adolescent pregnancy occurred in dinosaurs millions of years ago.

The dinosaurs were aged 8, 10 and 18, indicating they reached sexual maturity earlier than previously thought, according to Monday's online edition of Proceedings of the National Academy of Sciences.

In modern birds, medullary tissue lines bones for only a few weeks when they are producing eggs and is then reabsorbed. Finding it in dinosaurs, which are believed to be the ancestors of birds, sheds light on their reproduction also.

"This is an exciting finding, because age at sexual maturity is related to so many things," said the students' adviser, Kevin Padian, a professor of integrative biology and a curator in UC Berkeley's Museum of Paleontology.

The study was conducted by Sarah Werning, a graduate student at the University of California, Berkeley, and Andrew Lee, also a Berkeley grad student when the work was done. Lee is now a postdoctoral student at the Ohio University College of Osteopathic Medicine.

Werning said in a statement that pinpointing the age of reproductive maturity "opens up so many complementary avenues of dinosaur research. You can talk about dinosaur physiology, lifespan, and reproductive strategies. And you could use this technique to look at all kinds of extinct animals."

The medullary bones examined by Werning and Lee came from the meat-eater Allosaurus and the plant-eater Tenontosaurus. It's also been found in Tyrannosaurus rex, they said.

The research was done by the Geological Society of America, the Paleontological Society, the University of Oklahoma Graduate Student Senate, the Jurassic Foundation and U.C. Berkeley's Department of Integrative Biology.

(Agencies)