Hadrosaurus from Greek ἁδρός, hadros, meaning “bulky” or “large”, and σαῦρος, sauros, meaning “lizard”) is a valid genus of hadrosaurid dinosaur. The only known skeleton was discovered in 1858, representing the first dinosaur species known from more than isolated teeth to be identified in North America. In 1868, it became the first ever mounted dinosaur skeleton. Hadrosaurus foulkii is the only species in this genus and has been the official state dinosaur of New Jersey, United States since 1991.
Leidy recognized that these bones were from a dinosaur by their similarity to those of Iguanodon, discovered in England some decades before, but the skeleton of Hadrosaurus was far more complete. Leidy’s monograph Cretaceous Reptiles of the United States, describing Hadrosaurus more completely and with illustrations, was written in 1860, but the American Civil War delayed its publication until 1865.
Hadrosaurus was named the state fossil of New Jersey, designated in 1994. It is one of the most celebrated dinosaurs ever, and is of great historic importance.
When the skeleton was first assembled, it was displayed with a plaster skull sculpted by Hawkins. Many other artists have recreated Hadrosaurus with skulls from other, related species such as Gryposaurus and Brachylophosaurus. A statue of Hadrosaurus, sculpted by Haddonfield resident John Giannotti, now stands in the center of the town of Haddonfield, commemorating its discovery there.
In a 2008 study, Hadrosaurus was found to be more primitive than either lambeosaurines or other “hadrosaurines”, and not a particularly close relative of classic “hadrosaurines” such as Edmontosaurus and Saurolophus. As a result of this, the name Hadrosaurinae was restricted to Hadrosaurus alone, and the subfamily comprising the traditional “hadrosaurines” was renamed the Saurolophinae.
However, the latest phylogeny of the Hadrosauroidea indicates Hadrosaurus is definitely placed within the monophyletic group including all nonlambeosaurine hadrosaurids. Therefore, the traditional Hadrosaurinae should be still valid for designating all non-lambeosaurine hadrosaurids.
The holotype of Hadrosaurus was found in marine sediments, which suggests the skeleton was transported by a river and then deposited in the Cretaceous sea. The Hadrosaurus remains all persist to the Woodbury Formation.