New Jersey State Dinosaur: Hadrosaurus foulkii

The bones of Hadrosaurus foulkii had actually been noticed decades before the scientific excavation. In 1838, John Hopkins, a local businessman, found large bones in his marl pit on Creek Road in Haddonfield and kept them as curiosities. By the time he mentioned them to others, many had been lost or scattered. But the location was remembered.

In 1858, William Parker Foulke — a member of the Academy of Natural Sciences in Philadelphia and an enthusiastic amateur scientist — learned about the Hopkins bones and organized an excavation at the same site. Workers recovered a significant partial skeleton: vertebrae, limbs, teeth, and other elements. No skull, but far more substantial than any previous North American dinosaur find.

Foulke brought the bones to the Academy, where Joseph Leidy examined them. Leidy's formal description, published in 1858, named the species Hadrosaurus foulkii — 'Foulke's heavy lizard.' His key inference came from the skeleton's proportions: forelimbs significantly shorter than hindlimbs, suggesting the animal probably stood and moved bipedally, like a kangaroo. Leidy wrote this without a skull, without a complete specimen, and without any comparable animal to reference. The inference was correct.

Leidy's 1858 description is one of the most consequential papers in North American vertebrate paleontology. He was already the leading American anatomist of his generation when the Haddonfield bones arrived. His analysis was cautious and thorough — and the bipedal posture he inferred from skeletal proportions alone became the foundation for everything that followed in 1868.

Ten years after Leidy described the bones, Benjamin Waterhouse Hawkins — who had previously built the Crystal Palace dinosaur sculptures in London — mounted the Hadrosaurus foulkii skeleton at the Academy of Natural Sciences. The mount stood the animal upright on its hindlegs, with a plaster skull based on comparative anatomy. It was the first publicly displayed mounted dinosaur skeleton in history.

The impact was immediate and lasting. The popular image of dinosaurs as upright, active, large-bodied animals — rather than sprawling, lizard-like creatures — crystallized from this display. Museum administrators across America and Europe took note. Within a decade, mounted dinosaur skeletons were appearing in natural history museums in New York and London, all following the visual template established in Philadelphia by a New Jersey skeleton.

The original Hadrosaurus mount was eventually retired — the skeleton showed damage from the old mounting method. The bones remain at the Academy of Natural Sciences. A cast was returned to Haddonfield in 1984 and is mounted at the Haddonfield Public Library.

The Hadrosaurus foulkii discovery site in Haddonfield was designated a National Historic Landmark in 1994. The site on Maple Avenue — formerly Creek Road — is marked with a monument. A cast of the original bones returned to Haddonfield in 1984 and is mounted at the Haddonfield Public Library. The Haddonfield Historical Society was among the supporters of the 1991 state designation.

There are places where dinosaur bones were found earlier. There is no other site where the specific combination of specimen quality, scientific analysis, and subsequent public display created the visual vocabulary for 'what a dinosaur looks like' that persists today. The landmark designation recognizes that chain of events — the bones, Leidy's inference, and the 1868 mount together — not any single discovery in isolation.