Hadrosaurus

Hadrosaurus is a genus of duck-billed ornithopod dinosaur from the Late Cretaceous of eastern North America. The best-known species, Hadrosaurus foulkii, was described by paleontologist Joseph Leidy in 1858 from bones discovered by William Parker Foulke near Haddonfield, New Jersey. The specimen represented the first relatively complete dinosaur skeleton found in North America and was the subject of the first mounted dinosaur display in the United States (1868), making it an important icon in early paleontology.

Hadrosaurus is typically reconstructed as a large, herbivorous ornithopod that could move on both two and four legs. Estimates based on the preserved postcranial skeleton suggest a length of around 7 meters and a weight of several tonnes, though the skull of the type specimen is incomplete and many details of its appearance remain uncertain. Like other hadrosaurids, it is inferred to have had complex tooth structures adapted for processing plant material.

Taxonomically, Hadrosaurus has been important historically but is problematic in modern classification because the holotype lacks diagnostic cranial material. Many later finds from North America once assigned to Hadrosaurus have been reinterpreted or left indeterminate, so its precise relationships among hadrosauroids are still debated. Hadrosaurus foulkii is recognized for its scientific and cultural significance and is the state dinosaur of New Jersey.