New Jersey holds a unique position in the history of paleontology, serving as the location for some of North America’s earliest and most significant dinosaur discoveries. Before the famed bone rush of the American West, the state’s coastal deposits yielded fossils that fundamentally changed the scientific understanding of prehistoric life. These finds provided the first tangible proof that dinosaurs were not merely mythical creatures known only from scattered teeth and bone fragments. These discoveries established the groundwork for vertebrate paleontology in the United States and cemented the Garden State’s place in the narrative of deep time.
The Landmark Discovery of Hadrosaurus foulkii
The historical importance of New Jersey’s paleontology is centered on the 1858 excavation of Hadrosaurus foulkii in Haddonfield. A farmer had previously unearthed some gigantic bones in a marl pit on his property in 1838, but it was not until two decades later that the find received scientific attention. Lawyer and amateur naturalist William Parker Foulke, visiting the area, heard of the strange bones and organized a careful excavation of the site near the marl pit. Foulke uncovered a collection of 35 bones, including a nearly complete hind limb, pelvis, and parts of the forelimb and vertebrae.
He sent these remains to Dr. Joseph Leidy, a renowned anatomist at the Academy of Natural Sciences of Philadelphia. Leidy studied the fossils and, in 1858, formally named the creature Hadrosaurus foulkii, meaning “Foulke’s bulky lizard.” This was the first relatively complete dinosaur skeleton found in North America, unlike previous finds limited to teeth and small fragments. Leidy’s analysis showed that the creature possessed large hind limbs and much shorter forelimbs, suggesting it was bipedal rather than a sprawling, lizard-like animal.
This revolutionary concept was solidified in 1868 when a reconstructed skeleton of Hadrosaurus was mounted for public display in Philadelphia, becoming the first dinosaur skeleton ever mounted for exhibition in the world. The display, supervised by Leidy and constructed by artist Benjamin Waterhouse Hawkins, offered the public its first clear vision of a dinosaur as a massive, upright reptile. The Hadrosaurus discovery shifted the scientific perception of dinosaurs from slow, four-legged beasts to dynamic, two-legged animals, sparking global interest in paleontology.
Other Key Dinosaur Species Identified
Beyond the famed duck-billed dinosaur, New Jersey’s fossil record includes evidence of several other distinct dinosaur species that coexisted in the ancient coastal ecosystem. Among the most notable is Dryptosaurus, a carnivorous theropod that was a distant relative of Tyrannosaurus rex. The fragmented remains of this animal, excavated in 1866 from a marl pit, represent the first tyrannosauroid ever discovered in the United States, predating the famous Western finds.
The initial find of Dryptosaurus included a distinctive, large claw, which contributed to its early scientific name, Laelaps, and cemented its reputation as an active predator. Like many of the state’s dinosaur fossils, this find was incomplete, consisting primarily of limbs and pelvic bones. However, these fragments were enough to identify a large, meat-eating dinosaur.
Another group of dinosaurs found in the state are the Ornithomimids, or “ostrich dinosaurs,” which were swift, lightly built theropods. These dinosaurs, such as Ornithomimus, were characterized by long, powerful legs and a bird-like skull, suggesting they were among the fastest runners of their time. The identification of these and other species is often based on isolated teeth, vertebrae, and limb fragments, confirming that a diverse array of both herbivorous and carnivorous dinosaurs inhabited the area.
The Cretaceous Environment and Fossil Locations
The dinosaur fossils found in New Jersey date primarily to the Late Cretaceous period, roughly 100 to 66 million years ago, just before the mass extinction event. During this time, the geography of the state was vastly different from its modern appearance. Southern New Jersey existed as a shallow, submerged coastal plain, forming the edge of the Western Interior Seaway.
The terrestrial environment was a low-lying, subtropical region characterized by swamps, estuaries, and lush forests bordering the marine environment. This unique setting meant that the remains of land-dwelling dinosaurs like Hadrosaurus and Dryptosaurus were occasionally washed out to sea by ancient rivers and interred in marine sediments. The majority of the significant discoveries have been made in the greensand marl deposits of the New Jersey Coastal Plain.
These greensand deposits are rich in the mineral glauconite, which created an ideal environment for fossil preservation. The marl was historically mined for use as a fertilizer in the 19th century, and these commercial quarrying operations, known as marl pits, accidentally exposed numerous fossil layers. The sedimentary layers from the Navesink and Woodbury formations have yielded a wealth of fossils, preserving not only dinosaurs but also numerous marine creatures like mosasaurs, plesiosaurs, and ancient sharks.