Study: Dinosaurs had early pregnancies

ATHENS, Ohio, Jan. 16 (UPI) -- U.S. scientists have discovered dinosaurs often became pregnant as early as age 8, long before reaching their maximum adult size.

Ohio University and University of California-Berkeley researchers found medullary bone -- the same tissue that allows birds to develop eggshells -- in two new dinosaur specimens from different geologic periods: the meat-eater Allosaurus and the plant-eater Tenontosaurus. It's also been found in Tyrannosaurus rex.

The discovery pinpointed the age of the pregnant dinosaurs -- 8, 10 and 18 years -- suggesting dinosaurs reached sexual maturity earlier than thought, said Andrew Lee, an Ohio University doctoral student who conducted the work as a graduate student at the University of California-Berkeley with scientist Sarah Werning.

The new study suggested dinosaurs grew fast but only lived three to four years in adulthood. Offspring were probably precocious, like calves or foals, Lee said.

The research also offers more evidence that dinosaurs were less like reptiles and more like birds, he said. Although dinosaurs had offspring before adulthood, their early sexual maturity was more a function of their tremendous size than any anatomical similarity to crocodiles.

The study is reported in the Proceedings of the National Academy of Sciences.