for National Geographic News
Birdlike dinosaurs did not wait until they were fully grown to start having sex, a new study says.
Early sexual maturity is a trait associated with modern-day crocodiles more than birds—a surprise because most scientists believe birds are akin to modern dinosaurs. (Related: "Feathered" Dinosaur Was Bald, Not Bird Ancestor, Controversial Study Says" [June 1, 2007].)
Dinosaurs sit on eggs like birds, sleep like birds, and have bone structures like birds.
Given all these similarities, researchers thought they would find dinosaurs grew up and reproduced like birds, too.
Birds don't start mating until well after they are fully grown. Eagles, for example, reach full size in a year but don't mate until at least age four.
"That's clearly not what we're seeing in these dinosaurs," said lead study author Gregory Erickson, a paleontologist at Florida State University in Tallahassee.
(Erickson is also a host of the National Geographic Channel TV series Hunter and Hunted, and the National Geographic Society has partially funded some of his research. National Geographic News is part of the National Geographic Society.)
By mating early, dinosaurs are "really holding on to their ancestry, rather than jumping into the modern-bird style of reproduction," said study co-author Kristina Curry Rogers, a paleontologist at the Science Museum of Minnesota in St. Paul.
"Birds inherited only parts of their uniqueness from their dinosaur precursors, and everything else is distinctly bird."
The researchers studied the group of dinosaurs considered most birdlike—those that sit on eggs and may have had feathers.
A few fossilized handfuls of these so-called brooding, nonavian dinosaurs have been discovered in recent decades sitting on eggs.
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