Duck-Billed Dinosaurs "Outgrew" Their Predators

August 6, 2008

Talk about being a big baby.

The duck-billed dinosaur Hypacrosaurus grew three to five times faster than the fearsome predators that hunted it, reaching its full size by age ten, according to a new study.

Unlike other plant-eating dinosaurs, duckbills such as Hypacrosaurus didn't have piercing horns, dagger-like teeth, or hulking body armor.

So the ability to grow bigger faster provided the animals with a size advantage that likely served them well in their early years.

For example, baby duckbills were probably about the same size as Tyrannosaurus rex hatchlings, said study co-author Drew Lee of Ohio University's College of Osteopathic Medicine.

But by five years old the duckbill would be the size of a grown cow, while the T. rex would be only as big as a large dog.

"It's harder to hunt a larger animal, because it's physically dangerous," said study co-author Lisa Noelle Cooper of Kent State University and the Northeastern Ohio Universities College of Medicine.

"Growing Like Crazy"

Duck-billed dinosaurs, or hadrosaurs, were diverse and abundant in the late Cretaceous period, about 70 million years ago.

The soft-bodied animals flourished in what is now North America alongside many different meat-eating, two-legged dinosaurs known as theropods. (See a picture of the diversity of life in the Cretaceous.)

By counting and measuring rings in fossil leg bones, the researchers compared growth rates for Hypacrosaurus and three common theropods: the tyrannosaurs Albertosaurus and T. rex and the small velociraptor-like Troodon.

As with trees, each ring in the fossil bones represents a year of life. The wider the ring, the more growth occurred that year.

Continued on Next Page >>




NEWS FEEDS     After installing a news reader, click on this icon to download National Geographic News's XML/RSS feed.   After installing a news reader, click on this icon to download National Geographic News's XML/RSS feed.

Get our news delivered directly to your desktop—free.
How to Use XML or RSS

National Geographic Daily News To-Go

Listen to your favorite National Geographic news daily, anytime, anywhere from your mobile phone. No wires or syncing. Download Stitcher free today.
Click here to get 12 months of National Geographic Magazine for $15.