Bones in Our Backyard

Updated: Jun 25, 2021

It might be difficult to imagine Orange County without shopping malls, freeways, housing and people, but if we go back far enough in time the area was ruled by prehistoric creatures! The

Image: Ages of Rock by Ray Troll

fossil record of Orange County dates back to the Jurassic period, 199.6 to 145.5 million years ago, although findings from this period are extremely limited, as much of what are now the western states were under the sea. The majority of fossils found in the area are from the Miocene epoch, 23 to 5.3 million years ago, characterized by a warmer climate and an increase of land-dwelling creatures.

With what seems like nonstop construction and building projects requiring land assessments, it’s no wonder the volume of fossils unearthed in Orange County is immense! O.C. Park’s John D. Cooper Center preserves local fossils and has approximately 1.5 million unprocessed specimens in their collection. While there are many unknowns about the local fossil record, we have learned a great deal about the prehistoric inhabitants of the area.


Image:Natural History Museum

Present during the late Cretaceous period, the Hadrosaur, or duck-billed dinosaur, was a large,

Image: OC Parks

bipedal herbivore. In 1927, Bernard Nettleton Moore reported one of the earliest findings of a hadrosaur in Orange County. The discovery was made at the Ladd Formation in the Santa Ana Mountains. In 2017, the Augustynolophus, a genus of Hadrosaur, was designated as the official

state dinosaur of California.


Image: Science Museum Group, in the United Kingdom (Photo number: L0034207).

Ammonites, classified as Cephalopods, were marine animals that existed during the Age of the Dinosaurs. The fossils of these coiled mollusks are commonly found in the marine rock of the Ladd Formation. They went extinct at the end of the Cretaceous period.


The Imagotaria was one of the last surviving tuskless walrus from the Miocene. Instead of two long tusks, this pinniped had enlarged canines, indicating different feeding habits than extant

Image: Astronomy to Zoology

walruses. Although these creatures looked and behaved more like sea lions, they are classified

as walruses because of their skull and skeletal structure. One famous fossil discovered in Orange County is that of Waldo the Walrus. This fossil was found at a construction site and was damaged when a bulldozer hit its shoulder.


Photo: Xiaoming Wang

California’s first bear! The Phoberogale lived during the early Miocene and was only about the size of a racoon. Found in France, Pakistan, and California, the Phoberogale was one of the first bears to immigrate from Eurasia to the Americas. Fossils of the Phoberogale have been found in the Talega Bone Beds in San Clemente.

This is just a small sampling of the prehistoric creatures of Orange County! There are many organizations in the area that focus on paleontological and archaeological work and provide more information about the bones in our backyard! Check them out below!

The Cooper Center

The Southern California Paleontological Society

Cal State Fullerton Geological Science Department

Ralph B. Clark Regional Park Interpretive Center