Dinosaurs: Ancient Fossils, New Discoveries California Academy of Sciences Dinosaurs - Ancient Fossils, New Discoveries
Dinosaurs

Display or Defense?

Trophy Wall
Trophy Wall Exhibit
© AMNH

What's the Point?

Take one look at the massive skulls along this wall, with their sharp horns and spikes, and you might think these animals were aggressive, fierce fighters. But 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?


Pentaceratops
© John Sibbick

For many years, paleontologists thought these animals used their horns and spikes to fight predators like T. rex. The huge bony collars, or frills, around the animals' heads seemed to protect their necks. But upon closer examination, the frills are typically too thin to provide much protection. And among modern animals from beetles to bison, horns are almost always used to attract mates, compete with rivals or allow animals of the same species to recognize each other. In much the same way, the elaborate skulls of the horned dinosaurs may have been for display, not defense.

:: Learn more about this new view at AMNH ::

The Horned Dinosaurs

All of the dinosaurs displayed on this wall are "ceratopsian," or "horned-face," dinosaurs. The most famous ceratopsian is Triceratops, with its three horns. (You can touch the Triceratops horn on display here.) But Triceratops is just one member of this large family of dinosaurs, each with its own unique appearance.

A wide variety of reptiles, mammals and insects have horns or similar features. And in the vast majority of cases, these animals use their horns to recognize their species and compete for mates, not to fight off predators. Ceratopsian horns probably served the same purpose, with adult males locking horns in battles for females. The horns might have also been used to attract females.

:: Learn more about horned dinosaurs at AMNH ::

Stegasaurus
Stegasaurus
© John Sibbick

Colorful Display

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. Instead, the plates, which were covered in skin, may have been brightly colored; stegosaurs might have used the plates in dramatic courtship displays. Other kinds of stegosaurs had rows of spikes on their backs instead of plates.

Vanity Plates

The numerous grooves visible on some Stegosaurus plates provide evidence that blood vessels once crisscrossed the surface of the bone. Any wound to the plate would have bled considerably, making it unlikely that such plates were used to protect the animals. Instead, stegosaurs might have used plates in mating rituals or to help regulate body temperature.

:: Learn more about dinosaur mating display at AMNH ::

Protoceratops model
© AMNH

My, What a Big Skull You Have

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.

Paleontologists have identified more than 30 species of ceratopsian dinosaurs—and each species can be distinguished largely by features such as the shape of the frill or the number, size and position of the horns. In fact, scientists have speculated that perhaps the dinosaurs themselves relied on these features to recognize members of their own species. As a result, small changes in these features might have meant that members of the two populations would no longer mate, because they wouldn’t recognize each other. Such isolation would result in the emergence of new species, each one with a distinct appearance.

:: Learn more about skulls at AMNH ::

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