Daddy day care: dinosaur fathers guarded the eggs

By Will Dunham

WASHINGTON (Reuters) - You can call it dino daddy day care. Scientists who examined the fossilized remains of three types of medium-sized dinosaurs found with large clutches of eggs have concluded that the males rather than the females seem to have guarded the nests and brooded the eggs.

Writing on Thursday in the journal Science, they said this behavior is seen in certain existing species of birds. Scientists believe birds evolved from small, feathered predatory dinosaurs more than 150 million years ago.

The three types of dinosaurs, Troodon, Oviraptor and Citipati, lived roughly 75 million years ago and were theropods -- the primarily meat-eating group that also includes monstrous beasts like Tyrannosaurus rex and Giganotosaurus.

"There are a lot of characteristics that we once thought were unique to birds that are turning out not to be -- that they first arose in their theropod ancestors," Montana State University paleontologist Frankie Jackson, one of the researchers, said in a telephone interview.

The scientists said the findings suggest that at least in these types of dinosaurs, the males may have mated with several females that laid eggs in one large clutch. When the females left, the males incubated and protected the eggs on their own.

PATERNAL CARE

Male-only care for eggs occurs among certain large flightless birds like emus and rheas and the South American tinamous, according to fellow Montana State University paleontologist David Varricchio.

In these cases, the dinosaurs were found with an unusually large number of eggs -- each nest containing from 22 to 30 eggs. They were found in Montana in the case of Troodon, and Mongolia in the case of Oviraptor and Citipati.