Hadrosaurus

Hadrosaurus foulkii is historically significant as the first non-avian dinosaur named in North America. It also serves as the basis for the family Hadrosauridae and was the first articulated dinosaur skeleton mounted for public exhibition. This 1868 display in Philadelphia, overseen by Joseph Leidy and created by Benjamin Waterhouse Hawkins, showed for the first time that dinosaurs could be bipedal. This kangaroo-like posture challenged the earlier image of dinosaurs as exclusively quadrupedal. The original fossils were found in 1858 within a marl pit near Haddonfield, New Jersey.

Measuring around 7–8 m long, Hadrosaurus is technically classified as a basal hadrosauroid. Most modern studies place it just outside the family Hadrosauridae, even though the family bears its name. Because the holotype skeleton lacks a complete skull, detailed anatomical study has been difficult. Instead, our understanding of the animal comes from a partial postcranium that includes limb bones, ribs, vertebrae, and pelvic elements. Like its relatives, it likely possessed a broad beak, fleshy cheeks, and complex dental batteries for grinding plants. It was capable of moving on both two and four legs.

The Woodbury Formation, where the fossils were found, was a near-shore marine environment. The fact that the Hadrosaurus holotype was buried in marine sediments suggests the carcass washed out to sea after the animal died. As a generalist herbivore, its ecology was likely similar to that of more famous hadrosaurids like Edmontosaurus or Maiasaura. While the limited fossil material makes it hard to reconstruct specific behaviours, scientists use phylogenetic bracketing to infer that Hadrosaurus probably lived in herds, nested, and used its specialized teeth to process tough vegetation.

• ANSP 10005 — Leidy's holotype, Academy of Natural Sciences of Drexel University, Philadelphia.
• The 1868 mounted skeleton (now displayed in cast form) was the first articulated dinosaur in any museum.
• The Hadrosaurus Foulkii Leidy Site Park in Haddonfield commemorates the discovery.

Genus validity — Hadrosaurus foulkii is sometimes considered a nomen dubium because the holotype lacks diagnostic skull material at the genus level. Prieto-Márquez et al. (2006) re-examined the material and confirmed it as a valid genus, distinct from related hadrosauroids. Phylogenetic position — basal hadrosauroid outside Hadrosauridae proper despite being the family namesake.

Hadrosaurus is the official state dinosaur of New Jersey (designated 1991). The 1868 Philadelphia mount is a foundational moment in public dinosaur display. The dinosaur features prominently in New Jersey state historical materials and Haddonfield commemorative monuments.

• ornithopoda
• iguanodon
• parasaurolophus
• edmontosaurus
• lambeosaurus

• Leidy, J. (1858). Hadrosaurus and its discovery. Proceedings of the Academy of Natural Sciences of Philadelphia, 10, 213–218.
• Prieto-Márquez, A., et al. (2006). Re-evaluation of the type material of Hadrosaurus foulkii. Journal of Vertebrate Paleontology, 26, 760–764.
• Gallagher, W. B. (1995). Late Cretaceous dinosaur extinctions in the New Jersey Coastal Plain. Geological Society of America Special Paper, 290, 39–48.
• Horner, J. R., Weishampel, D. B., & Forster, C. A. (2004). Hadrosauridae. In The Dinosauria (2nd ed.).