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Dinosaurs in Southern California

Jun 23rd, 2021

Did you know that California has a state dinosaur? Or that the state was once covered by an ocean full of marine dinosaurs?

Yes! Dinosaurs are certainly a part of California's fascinating history, so if you live in our Southern California apartments then you’re going to want to hear more!

History of dinosaurs in California

Obviously, all our information about dinosaurs comes from fossils that paleontologists have discovered and are still discovering.

If your first thought is of the LaBrea Tar Pits in Los Angeles, then you may be slightly disappointed to know that there aren’t actually any dinosaurs there. Those tar pits formed just fifty thousand years ago, so all the fossils that come out of there are of trapped animals from a much more recent time period, like mammoths, saber-toothed cats and even dire wolves!

There is certainly an abundance of ancient fossils here in Southern California, but not all of them are dinosaurs. Most of them are prehistoric mammals, some are oceanic reptiles and sea creatures and some are birds, yet only a fraction of them are what we think of as dinosaurs.

Why? Well, before we dive into the history of dinosaurs in Southern California, it's important to define the specific era of prehistoric life that we're looking at. That will help us understand why Southern California lacks ample dinosaur remains, despite the definite existence of dinosaurs on the continent.

Basically, there are three major geological eras in which we further separate and categorize the history of our world’s current geological eon (the Phanerozoic eon). It’s the timeline of Earth since the earliest appearance of animal life around 541 million years ago (MYA). 

The first era is the Paleozoic era, which lasted from about 541 MYA to about 250 MYA . This era featured abundant early life in the forms of invertebrates, fish, mollusks and early tetrapods (four-legged creatures). 

The next era was the Mesozoic era, which is often called the Age of Reptiles or the Age of Conifers. This era stretched from around 250 MYA to about 66 MYA, during which reptiles thrived, significant tectonic movement occurred and the Earth's forests consisted largely of conifers and ferns. This era was ended by a mass extinction event that wiped out 75% of the planet’s plant and animal life. It’s thought that this event was caused by an asteroid impact on the Mayan Peninsula. 

The third and final era is the Cenozoic era, which is our current era stretching from 66 MYA to the present! This era features more birds, mammals and flowering plants than any other era and, of course, it’s where humans entered the scene! 

You’ve probably figured out that the dinosaurs lived during the Mesozoic era, and that the infamous asteroid impact was, in fact, one of the leading causes of these great reptiles’ extinction. Yet we still have very little evidence to show that there were dinosaurs here in SoCal, and most of that is due to late-stage tectonic activity.

Back in the Mesozoic era, most of California was covered by a mixture of shallow seas and dry land. The Sierra Nevada range had only just been formed by volcanic and tectonic activity, and much of the rest of the area was undergoing great shifts in geological formation. In the timeline of the entire world, these changes are considered more recent than others.

All that to say that the area known as modern-day California was fairly unstable and there wasn’t much dry land to nurture terrestrial dinosaurs. There were plenty of ocean animals and invertebrates, but not much in the way of "Jurassic Park" material. Thankfully, though, there are a few dinosaurs that we do know existed!

Dinosaurs found in California

While we have plenty of fossils from the era after the dinosaurs lived in, we only have a few that document the types of reptiles that called Southern California home during the Mesozoic era. And because so much of the land was covered by water, most of these SoCal fossils are the result of the dinosaurs’ bodies being washed out into the sea that once covered the state. 

Here are a few dinosaurs that we know lived here so long ago.


Californosaurus perrini

What a name! 

This is technically an ichthyosaur, meaning that it was a species of marine reptile or “fish lizard”. The Californosaurus prowled the waters both offshore and covering California, eating smaller fish and other ocean creatures. It never went on land, but it was a formidable creature at sea.

Shasta Lake in the Shasta-Trinity National Forest in Northern California is famous for the fossils of a similar, more evolved kind of ichthyosaur called the Shastasaurus!


Plotosaurus ‭‬bennisoni‭

Another marine reptile is the Plotosaurus. This was a species of mosasaur that existed after the similar ichthyosaurs, which lived earlier. A powerful swimmer, the Plotosaurus could grow up to 42 feet long and had the large eyes, powerful jaws and streamlined shape of a deadly ocean hunter. 


Aletopelta coombsi

Also called the “wandering shield,” the Aletopelta isn’t just one of the only dinosaur fossils to have been discovered in Southern California, but it’s also the only dinosaur species to have been originally discovered here, too! 

The name is derived from the hard, shield-like skin that covered the short-but-lengthy dinosaur. This dinosaur was a herbivore with a clubbed tail and hard skull that, along with the tough skin, protected it from carnivorous predators. 

The most interesting thing about the Aletopelta that was found is not necessarily what happened during its life, but its experience after death. The "wandering" nature of the name is not associated with its penchant for long walks on the beach, but rather because it was a land dinosaur whose fossilized remains were discovered at the bottom of an ancient sea. 

The theory is that the dinosaur died on land, after which its body was washed into the ocean by a flood or storm surge where it settled onto the ocean floor. For a while, this old dinosaur’s sunken bones became a home for a miniature coral reef before being covered by the ocean floor. 

Millions of years later, after the ocean had long since receded, paleontologists discovered the fossil of this gentle dinosaur that had wandered so very far from its home. Thus, the “wandering” name was bestowed.


Augustynolophus morrisi‭ 

The largest of the dinosaurs found in California, the 10-foot-tall Augustynolophus was one of the last dinosaur species to live on the planet before the fateful mass-extinction event that ended the Mesozoic era. 

This herbivorous dinosaur was discovered in the San Joaquin Valley and named after a Los Angeles family, the Augustyns, who supported the L.A. County Museum. It is also the official state dinosaur of California!

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Featured photo courtesy Pixabay/ DariuszSankowski

Author of Article

Colleen Ford is a South African who now lives in Spokane, Washington. She loves to travel, camp (in warm weather) and bake.

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