anatotitan

Anatotitan Fossil range: Late Cretaceous
Anatotitan copei at the American Museum of Natural History, New York
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Sauropsida Superorder: Dinosauria Order: Ornithischia Family: Hadrosauridae Subfamily: Hadrosaurinae Tribe: Edmontosaurini Genus: Anatotitan Chapman & Brett-Surman, 1990
Species
A. copei (type) A. longiceps (Marsh, 1897) Olshevsky, 1991

Anatotitan (a-NAT-o-TIE-tan; "duck titan") is a genus of hadrosaurid ornithopod dinosaur from the very end of the Cretaceous Period, in what is now North America. It was a very large animal, nearly 12 meters (40 feet) in length, with an extremely long and low skull.^[1] Anatotitan exhibits one of the most striking examples of the "duckbill" snout common to hadrosaurs.

Remains

This dinosaur is known from at least five specimens discovered in the U.S. states of South Dakota and Montana. Several of these specimens are extremely complete skeletons with well-preserved skulls. Several unique features were used to separate Anatotitan from other hadrosaurs when it was first described, many of them relating to its enormous skull. The skull is longer and lower proportionally than any other known hadrosaur, with one skull measuring over 1.18 meters (46 inches) long. The "duckbill" portion of the muzzle is also wider than in any other hadrosaur, almost as wide as the skull itself. Inside the mouth, there is a large diastema, or toothless section, which is also larger than in any other hadrosaur.

Remains of Anatotitan have been preserved in the Hell Creek and Lance Formations, which are dated to the late Maastrichtian stage of the Late Cretaceous Period, representing the last three million years before the extinction of the dinosaurs (68 to 65 million years ago).

Taxonomic history

Like many dinosaurs, Anatotitan has a long and somewhat confusing taxonomic history. The holotype, or original specimen, was a complete skull and skeleton found in 1882 by famous American paleontologist Edward Drinker Cope. Cope had previously discovered other specimens and placed them in the genus Diclonius, which was synonymized with Trachodon in 1902. Two of these extremely complete specimens were famously mounted side-by-side in the American Museum of Natural History in New York City under the name Trachodon mirabilis.

Meanwhile, another hadrosaur had been discovered in the western United States, which Othniel Charles Marsh named Claosaurus annectens in 1892. However, in 1942, paleontologists Richard Swann Lull and Nelda Wright recognized that this species was very different from the type species of Claosaurus and needed to have its own name. They created the new genus Anatosaurus ("duck lizard") and made Marsh's species the type species, calling it Anatosaurus annectens. Also, Lull and Wright recognized that the species Trachodon mirabilis was originally based on just a tooth and that the three skeletons referred to it in 1902 did not necessarily belong to the same species. A new species was created for them, which was called Anatosaurus copei, named after Edward Drinker Cope, who originally described the specimens.

Life restoration of Anatotitan copei.

Most modern paleontologists now include Anatosaurus annectens in the genus Edmontosaurus, as the species Edmontosaurus annectens. However, in 1990, paleontologists Ralph Chapman and Michael Brett-Surman argued that Anatosaurus copei was different enough from Edmontosaurus that it should be in a separate genus. Because the type species of Anatosaurus had already been synonymized with Edmontosaurus, a new generic name was needed. They created the name Anatotitan, from the Latin anas ("duck") and the Greek Titan, which was a race of mythological divine giants. This name refers both to the animal's size and to its wide "duckbill" snout.

The name Anatotitan was originally published in the Ph.D. thesis of Brett-Surman, but theses do not count as official publications according to ICZN regulations, so the official first publication of the name was in a separate 1990 paper authored by Chapman and Brett-Surman.

Today, debate continues as to whether Anatotitan copei should be in its own genus or whether it should be a species of Edmontosaurus. Some scientists believe that the Anatotitan specimens are in fact individuals of Edmontosaurus annectens whose skulls have been crushed during preservation and appear to be much longer and lower than they actually were (Horner et al., 2004).

Whether or not Anatotitan and Edmontosaurus are separate genera, they are very closely related and are both members of the subfamily Hadrosaurinae within the family Hadrosauridae. Shantungosaurus is another gigantic hadrosaur from China which may also be related to these North American dinosaurs.

Anatotitan in popular culture

Anatotitan as seen in Walking with Dinosaurs.

Although Anatotitan is not as well-known as many of its sister dinosaur taxa, the genus has appeared occasionally in popular media, and has become a representation of dinosaurs in popular culture. Anatotitan appeared in the final episode of the BBC documentary series Walking with Dinosaurs, "Death of a Dynasty".^[2] Director and producer Jasper James depicted Anatotitan as the last duck-billed dinosaur genus and as prey for the carnivorous theropod Tyrannosaurus rex. Anatotitan also appeared in the American nature documentary When Dinosaurs Roamed America as a peaceful herbivorous dinosaur.

References

• Brett-Surman, M.K., 1989. A revision of the Hadrosauridae (Reptilia: Ornithischia) and their evolution during the Campanian and Maastrichtian. Ph.D. dissertation, George Washington University, Washington, D.C.. pp.1-272.
• Chapman, R.E. & Brett-Surman, M.K. 1990. Morphometric observations on hadrosaurid ornithopods. In: Carpenter, K. & Currie, P.J. (Eds.). Dinosaur Systematics: Approaches and Perspectives. Cambridge: Cambridge University Press. Pp. 163-178.
• Horner, J.R., Weishampel, D.B., & Forster, C.A. 2004. Hadrosauridae. In: Weishampel, D.B., Dodson, P., & Osmolska, H. (Eds.). The Dinosauria (2nd Edition). Berkeley: University of California Press. Pp. 438-463.

External links

• Post on the Dinosaur Mailing List, detailing skepticism on the synonymy of Edmontosaurus and Anatotitan.

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