Display or Defense
Researchers have long wondered about the purpose of such peculiar features. Perhaps some served to protect the animal in battle. Others might have helped a dinosaur stay cool. More recently, scientists have come to another conclusion: Some of these features were likely used by dinosaurs in the competition for mates or to recognize members of their own species.
Dinosaurs are amazing animals-and sometimes quite bizarre. Among the many different species of dinosaurs, we find all sorts of strange body parts. Plates of armor. Exceptionally large or oddly shaped heads. Bony plates sticking out of the back-and bony horns sticking out of the front.
These dinosaurs, called ceratopsians, were slow-moving plant eaters that probably lived together in large herds-hardly the kind of animals you'd associate with deadly conflict. So why all the sharp points?
The most famous ceratopsian is Triceratops, with its three horns. But Triceratops is just one member of this large family of dinosaurs, each with its own unique appearance.
Its skull doesn't have any horns, but Psittacosaurus is also a member of the same group as Triceratops and other horned dinosaurs. The very first ceratopsians did not have horns or frills and probably looked much like Psittacosaurus.
Protoceratops, like most ceratopsians, had a large head compared to its body. One reason ceratopsian heads were so enormous is that the skulls had bony collars, known as frills, covering the neck. Like horns and spikes, frills came in all shapes and sizes.
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.
Dinosaurs are not the only animals with unusual features-think of a porcupine's quills or a peacock's tail. Indeed, many creatures have bizarre structures like horns, trunks, tusks, shells and more. Dinosaurs didn't stop with horns either, but had crests, spikes, domes, armor or plates.
The group of dinosaurs known as pachycephalosaursids had distinctive heads, with high, round skulls. Scientists once thought that modern bighorn sheep, with their two large, rounded horns, could provide a model for the behavior of dome-headed dinosaurs. But more recent research has overturned this idea.
The family of dinosaurs known as stegosaurs are well known for the two rows of bony plates along their backs. Researchers once thought these plates helped protect the animal from attack. But the plates were often very thin and contained numerous blood vessels, so they would have been too weak to serve as defensive features.
The armored dinosaurs, or ankylosaurs, were covered in bony plates, horns and spikes that formed a suit of armor from head to tail. Many of these features were almost certainly used for defense. But some features, like horns that pointed up, rather than out toward an oncoming predator, might have served another purpose: to make males more attractive to females.