triceratops n : huge ceratopsian dinosaur having three horns and the neck heavily armored with a very solid frill

English

Noun

1. Common name of the extinct genus Triceratops; a herbivorous ceratopsid from the late Cretaceous.

Triceratops () is an extinct genus of herbivorous ceratopsid dinosaur that lived during the late Maastrichtian stage of the Late Cretaceous Period, around 68 to 65 million years ago (mya) in what is now North America. It was one of the last dinosaur genera to appear before the great Cretaceous–Tertiary extinction event. Bearing a large bony frill and three horns on its large four-legged body, and conjuring similarities with the modern rhinoceros, Triceratops is one of the most recognizable of all dinosaurs. The name Triceratops, which literally means "three-horned face", is derived from the Greek tri/τρι- meaning "three", ceras/κέρας meaning "horn", and -ops/ωψ meaning "face". Though it shared the landscape with and was preyed upon by the fearsome Tyrannosaurus, it is unclear whether the two battled the way they are commonly depicted in movies, children's dinosaur books and many cartoons.

Although no complete skeleton has been found, Triceratops is well-known from numerous partial specimens collected since the introduction of the genus in 1887. The function of their frills and three distinctive facial horns has long inspired debate. Although traditionally viewed as defensive weapons against predators, the latest theories claim that it is more probable that these features were used in courtship and dominance displays, much like the antlers and horns of modern reindeer, mountain goats, or rhinoceros beetles.

Triceratops is the best-known of the ceratopsids, though the genus's exact placement within the group has been a point of contention amongst paleontologists. Two species, T. horridus and T. prorsus, are considered valid, although many other species have been named.

Description

Individual Triceratops are estimated to have reached about 7.9 to 9.0 m (26.0–29.5 ft) in length, 2.9 to 3.0 m (9.5–9.8 ft) in height, and 6.1–12.0 tonnes (13,000-26,000 lb) in weight. The most distinctive feature is their large skull, among the largest of all land animals. It could grow to be over 2 m (7 ft) in length, This conclusion does not preclude a sprawling gait for confrontations or feeding.

Classification

Triceratops is the best known genus of the Ceratopsidae, a family of large North American horned dinosaurs. The exact location of Triceratops among the ceratopsians has been debated over the years. Confusion stemmed mainly from the combination of short, solid frills (similar to that of Centrosaurinae), and the long brow horns (more akin to Ceratopsinae, also known as Chasmosaurinae). In the first overview of horned dinosaurs, R. S. Lull hypothesized two lineages, one of Monoclonius and Centrosaurus leading to Triceratops, the other with Ceratops and Torosaurus, making Triceratops a centrosaurine as the group is understood today. Later revisions supported this view, formally describing the first, short-frilled group as Centrosaurinae (including Triceratops), and the second, long-frilled group as Chasmosaurinae. In 1949, C. M. Sternberg was the first to question this and favoured instead that Triceratops was more closely related to Arrhinoceratops and Chasmosaurus based on skull and horn features, making Triceratops a ceratopsine (chasmosaurine of his usage) genus. However, he was largely ignored with John Ostrom, and later David Norman, both placing Triceratops within Centrosaurinae.

Subsequent discoveries and analyses upheld Sternberg's view on the position of Triceratops, with Lehman defining both subfamilies in 1990 and diagnosing Triceratops as ceratopsine (chasmosaurine of his usage) on the basis of several morphological features. In fact, it fits well into the ceratopsine subfamily, apart from its one feature of a shortened frill. Further research by Peter Dodson, including a 1990 cladistic analysis and a 1993 study using RFTRA (resistant-fit theta-rho analysis), a morphometric technique which systematically measures similarities in skull shape, reinforces Triceratops placement in the ceratopsine subfamily.

Use in phylogenetics

In phylogenetic taxonomy, the genus has been used as a reference point in the definition of Dinosauria; Dinosaurs have been designated as all descendants of the most recent common ancestor of Triceratops and Neornithes (i.e. modern birds). Furthermore, the bird-hipped dinosaurs, Ornithischia, have been designated as all dinosaurs with a more recent common ancestor to Triceratops than modern birds.

Origins

For many years the origins of Triceratops have been largely obscure. In 1922, the newly discovered Protoceratops was seen as its ancestor by Henry Fairfield Osborn, but many decades passed before additional findings came to light. However, recent years have been fruitful for the discovery of several dinosaurs related to ancestors of Triceratops. Zuniceratops, the earliest known ceratopsian with brow horns, was described in the late 1990s, and Yinlong, the first known Jurassic ceratopsian, in 2005.

These new finds have been vital in illustrating the origins of horned dinosaurs in general, suggesting an Asian origin in the Jurassic, and the appearance of truly horned ceratopsians by the beginning of the late Cretaceous in North America. As Triceratops is increasingly shown to be a member of the long-frilled Ceratopsinae subfamily, a likely ancestor may have resembled Chasmosaurus, which thrived some 5 million years earlier.

Discoveries and species

There has been much speculation over the functions of Triceratops head adornments. The two main theories have revolved around use in combat, or display in courtship, with the latter thought now to be the most likely primary function. This has been put forward by other authors over the years, but later studies do not find evidence of large muscle attachments on the frill bones.

Triceratops were long thought to have possibly used their horns and frills in combat with predators such as Tyrannosaurus, the idea being discussed first by C. H. Sternberg in 1917 and 70 years later by Robert Bakker. There is evidence that Tyrannosaurus did prey upon them, as a Triceratops pelvis has been found with tyrannosaur toothmarks and subsequent healing, indicating the wound was made while the animal was alive.

In 2005, a BBC documentary, The Truth About Killer Dinosaurs, tested how Triceratops might have defended themselves against large predators like Tyrannosaurus. To see if Triceratops could have charged other dinosaurs, as would a modern-day rhinoceros, an artificial Triceratops skull was made and propelled into simulated Tyrannosaurus skin at 24 km/h (15 mph). The brow horns penetrated the skin, but the blunt nose horn and the beak could not, and the front of the skull broke. The conclusion drawn was that it would have been impossible for Triceratops to have defended themselves in this way—instead they probably stood their ground when attacked by large predators, using their horns for goring if the predator came close enough.

In addition to combat with predators using horns, Triceratops are classically shown engaging each other in combat with horns locked. While studies show that such activity would be feasible, if unlike that of present-day horned animals, there is no evidence that they actually did so. Additionally, although pitting, holes, lesions, and other damage on Triceratops skulls (and the skulls of other ceratopsids) are often attributed to horn damage in combat, a recent study finds no evidence for horn thrust injuries causing these forms of damage (for example, there is no evidence of infection or healing). Instead, non-pathological bone resorption, or unknown bone diseases, are suggested as causes.

The large frill also may have helped to increase body area to regulate body temperature. A similar theory has been proposed regarding the plates of Stegosaurus, although this use alone would not account for the bizarre and extravagant variation seen in different members of the Ceratopsidae. A recent study of the smallest Triceratops skull, ascertained to be a juvenile, shows the frill and horns developed at a very early age, predating sexual development and thus probably important for visual communication and species recognition in general. The large eyes and shortened features, a hallmark of "cute" baby mammals, also suggest that the parent Triceratops may have cared for its young.

Depiction in recent popular media

The distinctive appearance of Triceratops has led to them being frequently depicted in films, computer games and documentaries. They appear in the film Jurassic Park, where one is portrayed as sick and is being treated by humans. They have also been featured in three major dinosaur documentaries: Walking with Dinosaurs, The Truth About Killer Dinosaurs and Prehistoric Park. They are famously known as "three-horns" (and are so named in The Land Before Time animated film and its numerous sequels) due to the three prominent horns on their head and nose, which have become almost synonymous with the dinosaurs. The shorthand "Trike" is another common informal name, and is also the name of the Triceratops character in the children's book series and television cartoon series Harry and His Bucket Full of Dinosaurs. Other TV series include Slag of Transformers fame, Dinosaucers, Dino-Riders and Dinozaurs. In the first series of Mighty Morphin' Power Rangers, the blue ranger's robot, called a "zord", took the shape of a triceratops, and the ranger's helmet was fashioned after the animal. thumb|left|Animatronic Triceratops facing a Tyrannosaurus. A recurring theme, especially in children's dinosaur books, is a climactic showdown or battle between Triceratops and T. rex. As such these two dinosaurs are often depicted and thought of as natural enemies. A memorable but anachronistic battle with Ceratosaurus substituting for T. rex is featured in the 1966 movie One Million Years B.C.

Triceratops appears in video games either derived directly from the Jurassic Park series or similarly themed, namely the 1997 PC games Jurassic Park: Chaos Island and Turok: Dinosaur Hunter, and the 2000 PC and Playstation game Dino Crisis 2. Triceratops also features in the Zoo Tycoon franchise. As well, it is a popular creature used in games designed by Nintendo, including Diddy Kong Racing and Starfox Adventures. Triceratops (the species are not identified) is also the official state fossil of South Dakota, and the official state dinosaur of Wyoming.

References

External links

• Triceratops in the Dino Directory
• Triceratops (short summary and good color illustration)
• Triceratops For Kids (a fact sheet about the Triceratops with activities for kids)
• Smithsonian Exhibit
• Dinosaur Mailing List post on Triceratops stance
• Listen to this article, Triceratops at the Internet Archive

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