Discoveries
Hadrosaurids were the first dinosaur family to be identified in North America, the first traces being found in 1855-1856 with the discovery of fossil teeth. Joseph Leidy examined the teeth, and erected the genera Trachodon and Thespesius (others included Troodon, Deinodon and Palaeoscincus). One species was named Trachodon mirabilis. Now it seems that the teeth genus Trachodon is a mixture of all sorts of cerapod dinosaurs, including ceratopsids. In 1858 the teeth were associated with Leidy's eponymous Hadrosaurus foulkii, named after the fossil hobbyist William Parker Foulke. More and more teeth were found, resulting in even more (now obsolete) genera.
A second duck-bill skeleton was unearthed, and was named Diclonius mirabilis in 1883 by Edward Drinker Cope, which he incorrectly used in favor of Trachodon mirabilis. But Trachodon, together with other poorly typed genera, was used more widely and, when Cope's famous "Diclonius mirabilis" skeleton was mounted at the American Museum of Natural History, it was labeled as "Trachodont dinosaur". The duck-billed dinosaur family was then named Trachodontidae.
A very well preserved complete hadrosaurid specimen (Edmontosaurus annectens) was recovered in 1908 by the fossil collector Charles Hazelius Sternberg and his three sons, in Converse County, Wyoming. Analyzed by Henry Osborn in 1912, it has come to be known as the "Trachodon mummy". This specimen's skin was almost completely preserved in the form of impressions.
Lawrence Lambe erected the genus Edmontosaurus ("lizard from Edmonton") in 1917 from a find in the lower Edmonton Formation (now Horseshoe Canyon Formation), Alberta. Hadrosaurid systematics were addressed in a 1942 monograph by Richard Swann Lull and Nelda Wright. They proposed the genus Anatosaurus for several species of dubious genera. Cope's famous mount at the AMNH became Anatosaurus copei. In 1990, Anatosaurus was moved to Edmontosaurus. One former Anatosaurus species was distinct enough from Edmontosaurus to be placed in a separate genus, named Anatotitan, so in 1990 the AMNH mount was re-labelled Anatotitan copei.
Paleontologists have found a hadrosaurid leg bone in Paleocene rocks, but it was probably reworked from a Cretaceous source.
One of the most complete fossilized specimens was found in 1999 in Hell Creek Formation of North Dakota and now is nicknamed "Dakota". The hadrosaur fossil is so well preserved that scientists have been able to calculate its muscle mass and learn that it was more muscular than thought, probably giving it the ability to outrun predators such as Tyrannosaurus rex. Unlike the collections of bones found in museums, this mummified hadrosaur fossil comes complete with skin (not merely skin impressions), ligaments, tendons and possibly some internal organs. It is being analyzed in the world's largest CT scanner, operated by the Boeing Co. The machine usually is used for detecting flaws in space shuttle engines and other large objects, but previously none as large as this. Researchers hope the technology will help them learn more about the fossilized insides of the creature. They also found a gap of about a centimeter between each vertebra, indicating that there may have been a disk or other material between them, allowing more flexibility and meaning the animal was actually longer than what is shown in a museum. Skin impressions have been found from the following hadrosaurs: Edmontosaurus annectens, Corythosaurus casuarius, Brachylophosaurus canadensis, Gryposaurus notabilis, Parasaurolophus walkeri, Lambeosaurus magnicristatus, Lambeosaurus lambei, Saurolophus osborni and Saurolophus angustirostris.
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