Triceratops: Facts About the Life and Times of a Three-horned Dinosaur

In 1887, Othniel Charles Marsh — the U.S. Geological Survey's official vertebratepaleontologist— received a fossilized animal brow withtwo large hornsthat a colleague had found near Denver, Colorado.

Unaware of the specimen's age, Marsh figured it came from a prehistoric bison, which he namedBison alticornis. Later discoveries proved the creature was actually a dinosaur far larger than any cow relative. One incomplete skull bearing three horns and a partial beak found its way to Marsh after someWyoming cowboyshad lassoed the thing, snapping off a horn in the process.

湿地被称为动物Triceratops, meaning "three-horned face," in an 1889scientific paper. Note that this is a genus name; under thesystemwe use to classify living things, a genus is one step above a species. So within the same genus, you can have multiple, closely-related species.

Today, two Triceratops species (both named by Marsh) are considered valid:Triceratops horridusandTriceratops prorsus.

Close attention is required to tell these animalsapart. All Triceratops had three-horned skulls, with two massive horns above the eye sockets and a smaller one over the nose. However, adultTriceratops prorsushad slightly longer nasal horns than their cousins did. Another difference? The beaks ofTriceratops prorsuslooked proportionately shorter.

We know both specieschanged as they aged. And not just in terms of overall body size. A bony frill protruded from the backside of every Triceratops skull. When these animals matured, their frills grew longer.

Often compared to medieval shields, these frills may have served adefensive purpose. Or maybe they evolved as communication tools; the structures could've been vibrantly colored, advertising the health and stamina of individual dinos.

三角恐龙幼仔有短而粗的眉角s above their eyes. These horns lengthened and curved backward during adolescence. But over time, a dramatic reversal took place; the horns straightened out and then bent forward in older specimens.

Maturity came with growth spurts. Thesmallestknown Triceratops skull — from a very young animal — is just 11.8 inches (30 centimeters) long. Other recovered skulls measuring well over 6.5 feet (2 meters) in length clearly belonged to adults.

Weighing an estimated 6.5 to 13 tons (6 to 12 metric tons), the biggest Triceratops were 29.5 feet (9 meters) long from nose to tail. The tips of their shoulders would've stood 9.8 feet (3 meters) off the ground.

Unlike alligators and monitor lizards, Triceratops held their arms and legs in a (more or less) verticalposition. Yet as Donald R. Prothero notes in his 2019 book "The Story of Life in 25 Fossils: Tales of Intrepid Fossil Hunters and the Wonders of Evolution," most Triceratops fingers didn't point dead ahead. Instead, these hand digits were angled away from the body. (Think "jazz hands.")

On top of the U.S. states we've mentioned, Triceratops fossils also occur inwest-central Canada. The genus first appeared around68 million years ago, near the tail end of a geologic period called the Cretaceous. Triceratops was still at large when a mass extinction closed out the Cretaceous 65.5 million years ago.

Thus, Triceratops has the distinction of being one of the last non-avian dinosaurs to ever evolve.

It was also a late-arrivingceratopsian. Distributed across Eurasia and North America, the ceratopsians were a group of plant-eating dinosaurs that predominantly lived in the Cretaceous. Known for their beaks and long, flaring cheek bones, they ranged frombipedal, dog-sized animals to ... well, giant quadrupeds like Triceratops. Many had horns and/or frills, arranged in a spectacular array of different combinations.

Triceratops belonged to the chasmosaurinae, a major subgroup of these dinoscharacterizedmainly by their elongated snouts (among other features).

Large eyebrow horns were another common trait among the chasmosaurines, Triceratops included. Lesions and fractures are regularly seen on Triceratops frill and cheek bones. These could indicate that the animals used their brow horns in one-on-one combat with each other.

The jury's still out on whether or not Triceratops moved inherds. But we have a pretty good idea of what the creatures ate. Their teeth were arranged in so-called "dental batteries." Every individual tooth was stacked in a vertical column of three to five teeth. And these formed rows, with 36 to 40 tooth-loaded columns occurring side by side. Altogether, a single Triceratops could have800 teethat its disposal.

With its narrow beak, powerful jaws and replaceable (self-sharpening) teeth, Triceratops probably fed oncycadsand other tough, fibrous plants.

Ah, but what ate Triceratops? Well, we knowTyrannosaurus rexlived in the same time and place — and it occasionally made a meal of the big herbivore. Bite marks matching T. rex's distinctive teeth have been found on several Triceratops skeletons, with the frills and faces getting more than their fair share of the injuries.

Pointing to these scars, some have argued that T. rex would methodicallyrip the heads offdead Triceratops. By grabbing ahold of the frills and tugging, the predators could decapitate the bodies, exposing choiceneck musclesbelow. Nothing beats a hard-earned meal.