Developments in Brief : Colorado Paleontologist Believes Brontosaurus Young Were Born Live

Most paleontologists believe that all dinosaurs were reptiles that hatched from eggs. But Robert Bakker, curator of paleontology at the University of Colorado Museum, no longer can be counted among them.

“I’ve spent years looking for brontosaurus eggs, and there should be plenty of evidence. But there’s none,” he said.

Bakker now believes that brontosaurus babies were born live, weighing 200 to 300 pounds, and that they were nurtured within the protection of a herd of adults much like modern-day elephants. His theory appears in a recent issue of the museum’s journal, Hunteria.

Bakker noted that scientists have never found evidence of a brontosaurus nest even though they’ve found nests of other types of dinosaurs.

“You find a high mortality with the egg-laying method of reproducing,” he said. “There should be lots of little brontosaur bones lying around . . . but the smallest brontosaur ever discovered was already about one-fourth the size of an adult.”

The massive brontosaurus, which lived 125 million years ago, is one of the largest of the dinosaurs, reaching 35 feet in length. Brontosauruses had wide bodies, tiny heads at the end of long necks and sweeping tails.

Bakker also said 40 or 50 sets of adult remains of the brontosaurus show that they had sufficiently wide pelvic canals to give birth. He said most other dinosaurs had small pelvises that would have prevented live births.

“The most compelling evidence is the bones of a mother dinosaur with a fetus within it,” he said. “It was found in 1910 and they have been trying to explain it away ever since as a smaller, unclassified dinosaur whose bones got washed in with the brontosaur. I think it’s very clear it was a fetus.”

Bakker said he believes brontosauruses raised their young in herds because their fossilized footprints have been found all over the world.

“They are herd footprints and right in the middle are little baby footprints,” he said. “Obviously they were right underfoot where they could be protected.”