Written by Ria Sarkar, M.S. Student in the Rutgers Department of Earth and Planetary Sciences

Did you know that New Jersey has its own state fossil? Yes, you read that right! And even better, it’s a dinosaur!

Hadrosaur Model ImageThe Hadrosaurus foulkii was the first mostly complete dinosaur skeleton ever found in North America and marked a significant moment in the field of vertebrate paleontology in the late 1800s.

The Hadrosaurus is part of the Hadrosauridae subfamily and is closely related to Iguanodontids. The name Hadrosaurus translates to “heavy lizard” or “bulky lizard” in Greek and the species name foulkii was named for the discoverer, William Parker Foulke. These dinosaurs first appeared about 100 million years ago during the Middle Cretaceous Period and are considered to be one of the most successful herbivorous groups at the end of the Cretaceous (Lucas, 2007). Their geographic distribution was not limited to just North America; they were found on all continents including Antarctica!

Hadrosaurus foulkii Public Domain

In the late 1830s, a farmer named John Estaugh Hopkins was digging in a marl pit in Haddonfield, NJ. It is there that he began finding large bones of an unidentified creature. He did not think too much of it and even gave some bones away to curious visitors (Sadurni, 2016). More than 20 years later in 1858, William Parker Foulke, a lawyer and amateur geologist, joined Hopkins for dinner at his home. Hopkins showed him the strange bones he had found 20 years earlier and with his permission, Foulke began an excavation. He invited his friend, Philadelphia anatomist and founder of vertebrate paleontology, Dr. Joseph Leidy, to join him. Together they retrieved a nearly complete dinosaur skeleton with only the skull missing. They measured the femur at an astonishing length of 4 feet and estimated that Hadrosaurus foulkii must have been at least 25 feet long (Cope, 1867; Thomson, 2008).

Marveling at the sheer size of this creature, Leidy believed this was a dinosaur very similar to the recently discovered Iguanodon. Noting the orientation of the pelvis, Leidy believed this new specimen was bipedal with an upright posture, unlike the sprawling posture of Iguanodon. This was revolutionary at the time as it changed the understanding of dinosaur appearance and posture (Lucas, 2007). However, scientists now believe that Hadrosaurus was a facultative biped, meaning that it normally walked on four legs, but could also walk on its two hind legs when necessary.


Hadrosaur Family Tree Debivort CC BY SA 3.0The Hadrosaurus is a genus of the Hadrosaurid dinosaurs, which are known as duck-billed dinosaurs for their mouths that resemble toothless beaks. They had incredibly strong jaws in addition to hundreds of teeth arranged in intricate “dental batteries” adapted to grind fibrous plants. Since the skeletons of most hadrosaurid species lack variation, their skulls are primarily used to distinguish between them. For example, some hadrosaurids had large bony crests on the top of their heads. An early suggestion for the function of these head crests was an air reserve to allow the dinosaur to stay underwater. In addition to the duck-like beak and possible webbed feet (which later turned out to be impressions left by soft tissue), this idea of an air reserve led to the belief that Hadrosaurus was a marine animal. However, scientists now agree that Hadrosaurus was a terrestrial animal and that the head crest was primarily used to make low-frequency calls for long distance communication.


Hadrosaur Painting

While the original skeleton of Hadrosaurus foulkii is mounted at Drexel University’s Academy of Natural Sciences, the Rutgers University Geology Museum also has a display dedicated to the beloved state dinosaur. Our Hadrosaur display contains a 19th century painting by Robert Bruce Horsfall (1869-1948), who was a New Jersey resident and wildlife illustrator. His painting (image to right) depicts a pair of Hadrosaurs roaming a marsh-like habitat (Sanchez, 2001). The posture of the Hadrosaurs is true to the early beliefs that the Hadrosaurus was bipedal and dragged its tail on the ground as it walked. However, modern reconstructions suggest that Hadrosaurus held its body in a more horizontal position with the tail held out for balance. Also on display below the painting is the ankle bone, or astragalus, of a Hadrosaurus. The primary function of this bone is to distribute the weight of the body to the rest of the foot.

Despite all we know about this dinosaur, many questions still remain to be answered, and our view and knowledge of Hadrosaurus will continue to change as we learn more about Earth’s ancient life. There are still plenty of mysterious dinosaurs buried underground, just waiting to be uncovered, maybe even in your own backyard!


Image Credits

Image 1: Rutgers University Geology Museum

Image 2: Public Domain via Wikimedia Commons

Image 3: Debivort via Wikimedia Commons, License CC BY-SA 3.0, no modifications made.

Image 4: Rutgers University Geology Museum



Cope, E. (1867). The Fossil Reptiles of New Jersey. The American Naturalist, 1(1), 23-30. Retrieved May 29, 2020, from www.jstor.org/stable/2447336

Lucas, S.G. (2007). Dinosaurs: The Textbook (5th ed.). McGrawHill.

Perrin, H. (2018, November 16). Jersey’s Fossil History Shows that Giants Lived Here. Retrieved May 29, 2020, from https://njmonthly.com/articles/historic-jersey/fossils-giants-lived-here/

Sadurni, L. F. (2016, December 12). The discovery 158 years ago that put Haddonfield in the history books. Retrieved May 29, 2020, from https://www.inquirer.com/philly/news/new_jersey/20161212_The_discovery_158_years_ago_that_put_Haddonfield_in_the_history_books.html
Sanchez, K. (2001). Robert Bruce Horsfell. Retrieved May 29, 2020, from https://www.kellscraft.com/horsfallbio.html

Thomson, K. (2008). The Legacy of the Mastodon: The Golden Age of Fossils in America. Yale University Press. Retrieved May 29, 2020, from www.jstor.org/stable/j.ctt1np975