Herd Mentality

Most dinosaur bones are found piece by piece--a broken Stegosaurus thigh bone here, a T. rex tooth there. When paleontologists uncover a nearly complete skeleton, they are thrilled--and finding fossils of dozens of dinosaurs of the same species in the same location is like winning the lottery. Luckily for scientists who study horned dinosaurs, fossil remains of these animals have often been found in such dinosaur graveyards.

What causes dinosaur graveyards to form? In most cases, the victims died at essentially the same time--killed crossing a river or after a volcanic eruption, perhaps. Dinosaurs found grouped together in death may have lived together in groups as well. Paleontologists think that members of certain species of horned dinosaurs lived in large herds much like modern elephants or zebras.

New Idea: Watching Dinosaurs Grow Up

Dinosaur graveyards have been very important to the study of ceratopsian dinosaurs, thanks to the hundreds or even thousands of animals of all ages and sizes buried in them. Paleontologist Scott Sampson has used fossils found in these large bone beds to study how ceratopsian horns and frills changed shape as the animals grew up.

Sampson analyzed skulls of horned dinosaurs of all ages, starting when the animals were less than a year old. He found that young ceratopsians typically had very simple horns. These features took their final form only when the animals reached adult size. If the function of fully developed horns and frills was to protect dinosaurs, we would expect to see them on the younger, more vulnerable animals.

Fast Facts: Anchiceratops

Species: Anchiceratops ornatus
Pronunciation: "ank-ee-SAIR-uh-tops oar-NAY-tus"
LENGTH: 6 meters (20 feet)
WEIGHT: probably 1 ton or more
Food: plants
When it lived: 70 million years ago
Fun fact: Anchiceratops seems to have preferred low-lying, marshy habitats.