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Dinosaurs Had Teen Pregnancies, Too

Findings show that, like humans, they reached sexual maturity early to improve odds of survival

MONDAY, Jan. 21, 2008 (HealthDay News) -- Dinosaurs experienced rapid growth during adolescence and reached sexual maturity near the end of this growth spurt, before they reached maximum body size, say University of California, Berkeley, scientists.

They noted that humans and other medium-to-large mammals are also able to reproduce before they finish growing. This does not occur in reptiles.

This finding about dinosaurs suggests that they suffered high death rates as adults, which made sexual maturity at an early age necessary for species survival. The study was published online in the journal Proceedings of the National Academy of Sciences.

"This is an exciting finding, because age at sexual maturity is related to so many things. It also shows that you can't use reptiles as a model for dinosaur growth, as many scientists still do," Kevin Padian, a professor of integrative biology and a curator in UC Berkeley's Museum of Paleontology, said in a prepared statement. He was adviser to the students -- Sarah Werning and Andrew H. Lee -- who conducted the study.

Werning and Lee analyzed fossilized bones from adolescent female dinosaurs and identified a layer of calcium-rich bone tissue (medullary bone) that's deposited in the marrow cavity just before egg-laying as a resource for making eggshells. This showed the dinosaurs were sexually mature.

Medullary bone is found in female birds.

"We were lucky to find these female fossils. Medullary bone is only around for three to four weeks in females who are reproductively mature, so you'd have to cut up a lot of dinosaur bones to have a good chance of finding this," Werning said in a prepared statement.

More information

The Dinosaur Institute at the Natural History Museum of Los Angeles County has more about dinosaur reproduction and development.

SOURCE: University of California, Berkeley, news release, Jan. 14, 2008
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