With its three horns and giant frill, the triceratops is one of those outsize dinosaurs that have captured the public's imagination almost as much as Tyrannosaurus rex. But later discoveries about triceratops—including that it had only two real horns—might surprise you. Here are 10 facts about the once-mighty plant-eater:

01 of 10 Two Horns, Not Three LEONELLO CALVETTI/SCIENCE PHOTO LIBRARY / Getty Images Triceratops is Greek for "three-horned face," but this dinosaur actually had only two genuine horns; the third, a much shorter "horn" on the end of its snout, was made from a soft protein called keratin, the kind found in human fingernails, and wouldn't have been much use in a tussle with a hungry raptor. Paleontologists have identified the remains of a two-horned dinosaur called Nedoceratops (formerly Diceratops), but it may represent a juvenile growth stage of Triceratops.

02 of 10 Skull Was One-Third of Its Body Triceratops skeleton displayed at the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania. Richard Cummins / Getty Images Part of what makes a triceratops so recognizable is its enormous skull, which, with its backward-pointing frill, could easily attain a length of over seven feet. The skulls of other ceratopsians, such as Centrosaurus and Styracosaurus, were even bigger and more elaborate, probably as a result of sexual selection, as males with bigger heads were more attractive to females during mating season and passed down this trait to their offspring. The biggest skull of all horned, frilled dinosaurs belonged to the allusively named Titanoceratops.

03 of 10 Was Considered Food for Tyrannosaurus Rex A Triceratops meets up with two hungry T. rex dinosaurs during a meteor shower. Joe Tucciarone / Science Photo Library / Getty Images As dinosaur fans know, Triceratops and Tyrannosaurus rex occupied the same ecosystem—the marshes and forests of western North America—about 65 million years ago, just before the K-T extinction that wiped out the dinosaurs. It's reasonable to assume that T. rex occasionally preyed on Triceratops, though only Hollywood special-effects wizards know how it managed to evade this plant eater's sharp horns.

04 of 10 Had a Hard, Parrotlike Beak Close-up profile of a Triceratops showing pebbly patterned skin and parrotlike beak. Stéphane Bernard / Getty Images One of the lesser-known facts about dinosaurs such as Triceratops is that they had birdlike beaks and could clip off hundreds of pounds of tough vegetation (including cycads, ginkgoes, and conifers) every day. They also had "batteries" of shearing teeth embedded in their jaws, a few hundred of which were in use at any given time. As one set of teeth wore down from constant chewing, they would be replaced by the adjacent battery, a process that continued throughout the dinosaur's lifetime.

05 of 10 Ancestors the Size of Big House Cats A couple of plant-eating Triceratops roam through lush green wilderness. De Agostini Picture Library / Getty Images By the time ceratopsian dinosaurs reached North America, during the late Cretaceous period, they had evolved to the size of cattle, but their distant progenitors were small, occasionally bipedal, and slightly comical-looking plant-eaters that roamed central and eastern Asia. One of the earliest identified ceratopsians was the late Jurassic Chaoyangsaurus, which weighed 30 pounds and had only the most rudimentary hint of a horn and frill. Other early members of the horned, frilled dinosaur family may have been even smaller.

06 of 10 Frill Signaled Other Herd Members Triceratops joins other creatures at a watering hole at sunset. Mark Garlick / Science Photo Library / Getty Images Why did Triceratops have such a prominent frill? As with all such anatomical structures in the animal kingdom, this thin flap of skin over solid bone likely served a dual (or even triple) purpose. The most probable explanation is that it was used to signal other members of the herd. A brightly colored frill, flushed pink by the numerous blood vessels under its surface, may have signaled sexual availability or warned of the approach of a hungry Tyrannosaurus rex. It may also have had some temperature-regulation function, assuming that Triceratops were cold-blooded.

07 of 10 Probably the Same as Torosaurus The horned Torosaurus looked similar to Triceratops males. Nobumichi Tamura / Stocktrek Images / Getty Images In modern times, many dinosaur genera have been reinterpreted as "growth stages" of previously named genera. This appears to be true with the two-horned Torosaurus, which some paleontologists argue represents the remains of unusually long-lived Triceratops males whose frills continued to grow into old age. But it's doubtful that Triceratops genus name will have to change to Torosaurus, the way Brontosaurus became Apatosaurus.

08 of 10 The Bone Wars A herd of Triceratops crossing a dry desert. Mark Garlick / Science Photo Library / Getty Images In 1887, American paleontologist Othniel C. Marsh examined a partial Triceratops skull, complete with horns, discovered in the American West and incorrectly assigned the remains to the grazing mammal Bison alticornis, which didn't evolve until tens of millions of years later, long after dinosaurs were extinct. Marsh quickly reversed this embarrassing blunder, though more were made on both sides in the so-called Bone Wars between Marsh and rival paleontologist Edward Drinker Cope.

09 of 10 Fossils Are Prized Collector's Items Stephen J. Krasemann / Getty Images Because the skull and horns of triceratops were so large, so distinctive, and so resistant to natural erosion—and because so many specimens were discovered in the American West—museums and individual collectors tend to dig deep to enrich their collections. In 2008, a wealthy dinosaur fan purchased a specimen named Triceratops Cliff for $1 million and donated it to the Boston Museum of Science. Unfortunately, the hunger for Triceratops bones has resulted in a thriving gray market, as unscrupulous fossil hunters tried to poach and sell this dinosaur's remains.