Anatotitan or “large duck” is a genus of flat-headed dinosaur commonly referred to as a “duck-billed dinosaur”. It lived during the end of the Cretaceous Period, in what is now North America. Its remains have been preserved in the Hell Creek and Lance Formations dated 68 to 65 mya. They were among the last dinosaurs that existed on the planet before the extinction of all dinosaurs 65 million years ago.

Like many dinosaurs, the history of Anatotitan is somewhat confusing. The original specimen on which the genus is based, was found in 1882 by Dr. J. L. Wortman and R. S. Hill working under paleontologist Edward Drinker Cope. This specimen, which was found north of the Black Hills of South Dakota, had numerous skin impressions. It was missing part of the pelvis and torso. Originally, Cope assigned this discovery to the genus Diclonius. After Joseph Leidy abandoned his work on Trachodon, Cope assigned it to this genus. Eventually, Cope’s descriptions were updated when rival Othniel Charles Marsh published his findings based on the a lower jaw recovered by John Bell Hatcher in 1889 from the Lance Formation in Wyoming. Marsh named this partial jaw Trachodon longiceps. It was found that this jaw shared prominent ridges running along the side just like Cope’s specimen, although it was much larger. Another nearly complete skeleton was found by rancher Oscar Hunter in Hell Creek Formation in 1904. After debate of its authenticity, it was turned over to Barnum Brown, who excavated it in 1906 for the American Museum of Natural History. This specimen allowed for Cope’s restoration of his remains and in 1907 the two specimens were mounted side-by-side in the American Museum of Natural History under the name T. mirabilis.

The length of Anatotitan is estimated at about 38 feet long, with a head about 3.87 feet long. The estimate of its length was later downsized to about 29 feet long, although in fairness to the nominate estimate, about a dozen vertebrae, the hips, and thigh bone had been carried away by a stream cutting through the remains, and the tip of the tail was incomplete. The weight has been estimated to be about 3.3 tons. The skull of the Anatotitan was long, with a wide muzzle, and resembled the bill of a goose or spoonbill. The nostril openings formed deep pockets. The eye sockets were rectangular and longer front to back than top to bottom. The top of the skull was flat and lacked a bony crest. The vertebrae system consisted of twelve neck, twelve back, nine sacral, and thirty tail vertebrae. It had long limbs and could move both on four legs or two legs. It most likely foraged for food on four legs, but ran on two.

Anatotitan was a large herbivore. It ate plants with a sophisticated jaw system that allowed it to grind food through analogous chewing motions. The teeth were continually replaced by new ones and were contained within dental batteries that contained hundreds of teeth. It would cut plant matter with its broad beak and then held in its mouth with a strong jaw. It is believed that it at anything from the ground up to about 13 feet from the ground.

Anatotitan remains are known mostly from the late Maastrichtian Age rocks from South Dakota and Montana. No bone beds of multiple individuals have been recorded as of yet. The area where the two original specimens were recovered has been described by Dale Russell as an environment with flat floodplains and a relatively dry subtropical climate that supported a variety of plants ranging from angiosperm trees, to cedars and bald cypress, to ferns and ginkgos. Other dinosaurs that shared its time in this place included Ankylosaurus, Edmontosaurus, Torosaurus, Triceratops, and Tyrannosaurus, as well as others.

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