The Only Dinosaur That Lived in Washington (And Where to See Fossils Today)

Written by Kellianne Matthews
Updated: June 1, 2023
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From the lush forests of Seattle to the high peaks of Mount Rainier, Washington is a state full of awe and wonder. But what many visitors may not know is that it was also home to some of the most incredible plants and creatures in prehistoric times! Washington boasts an incredible fossil record that spans virtually the entire geologic timeline. The state’s fossil record showcases a wide array of preservation types — from bones to petrified wood and more. It’s truly a remarkable place for prehistoric discovery. So, let’s take a closer look at the only dinosaur that lived in Washington, and where to see fossils today!

A Mysterious Therapod

The only dinosaur that has ever been found in Washington State was a therapod from 80 million years ago. Researchers only found the dinosaur’s partial left femur. However, it was enough to determine that the fossil came from a two-legged, meat-eating therapod, similar to the tyrannosaurus rex and the velociraptor. 

This dinosaur fossil in Washington is from the Late Cretaceous period and is around 80 million years old. It is 16.7 inches long and 8.7 inches wide, but unfortunately it’s not complete, so scientists can’t tell what family or species it belonged to. However, they analyzed specimens from other museums and found that the full size of the femur would have been more than 3 feet long. That’s just a bit shorter than the femur of a tyrannosaurus rex.

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The Burke Museum research team collected the fossil in May 2015 along the shore of Sucia Island State Park in the San Juan Islands. Fossilized prehistoric clams were discovered inside the hollow part of the femur bone, suggesting the dinosaur fossilized in marine rock. This is quite a rare occurrence and it provides scientists with a glimpse into what other life forms might have been present when the dinosaur was fossilized.

Unlike the mysterious therapod, paleontologists were able to identify the species of these fossilized clams, Crassatellites conradiana. The clams lived in shallow water, so it’s likely the dinosaur died near the water and the waves eventually washed it into the sea.


The only dinosaur fossil ever found in Washington came from a therapod. Therapods are two-legged, meat-eating dinosaurs like the tyrannosaurus rex and the velociraptor. 


Other Fossils in Washington

Dinosaurs lived from 240 to 66 million years ago, and during this time period, Washington was mostly underwater. There was very little exposed rock in Washington at that time, so it is rare to find dinosaur fossils. That’s what makes Washington’s therapod fossil a very special and lucky discovery!

However, Washington is home to many other types of extremely well-preserved fossils. The state has a special fossil record that covers most of the Earth’s history and includes many different kinds of fossils. Let’s take a look at some of these in detail.

Columbian Mammoth (Mammuthus columbi)

Washington’s official state fossil is the Columbian mammoth. The Columbian mammoth was an impressive creature that roamed parts of North America during the Pleistocene period. It was a member of the elephant family and had distinctive curved tusks that could measure up to 16 feet long! This gargantuan mammal also had long, curling hairs on its body and a tail measuring 5 to 6 feet in length. The Columbian mammoth was even larger than the woolly mammoth. It stood around 13 feet tall at its shoulders and weighed 22,000 pounds! 

Columbian Mammoth

The Columbian mammoth lived in warmer regions of North America during the Pleistocene.

©Daniel Eskridge/


Fossils from marine animals do not stand the test of time quite like those of land animals. However, fossils from a very unique prehistoric whale were discovered in Washington! Chonectus was an aquatic mammal with large flippers and a tail like a fish. 

Chonecetus was a special creature that had both teeth and baleen plates in its mouth. It could both eat big fish and filter tiny plankton from the water — making it an important evolutionary discovery!


In 1935, a group of hikers in Washington found the fossils of a small, rhinoceros-like creature that they called the Blue Lake Rhino. The Blue Lake Rhino lived 15 million years ago. Although we’re not exactly sure what species it was, scientists think it could a diceratherium, the ancestor of the double-horned rhino. However, the Blue Lake Rhino only had two tiny horns on its nose — one on each side.

Giant Ground Sloth

In 1961, construction workers were working on the Sea-Tac International Airport when they stumbled upon a collection of ancient bones! Scientists from the Burke Museum came to look and found more bones. They uncovered enough to make up almost 60% of a giant ground sloth called Megalonyx jeffersonii. This fascinating creature lived around 12,600 years ago and weighed about one ton!

Most of the time you need to chip old bones out of hard dirt, but the giant sloth found at Sea-Tac was in perfect condition. You could even see the little marks in the bones left from the muscles!

An interesting fact about the giant ground sloth is its scientific name came from U.S. President Thomas Jefferson! Jefferson had received bones of a giant ground sloth from Colonel John Stewart, including its radius, ulna, and claws. In a speech to the American Philosophical Society on March 10th, Jefferson called the creature Megalonyx jeffersonii (or “great-claw”). 

giant ground sloth

, a type of giant ground sloth, once lived all throughout the United States.

©Aunt Spray/

Trilobites and Ammonites

Washington State is a great place to look for fossils — especially trilobites and ammonites. Trilobites are an ancient type of arthropod from the Paleozoic Era, and you can find them just about everywhere in the state. Ammonites are related to the nautilus but have a much more intricate shell pattern. They can be found in abundance along the fossil-rich coastline of Washington. During the Paleozoic and Mesozoic eras, these small- to medium-sized invertebrates were an essential part of the marine food chain.


Trilobites are a fossil group of extinct marine arachnomorph arthropods.


Petrified Wood

Here’s a really cool fact: petrified wood is Washington’s official State Gem! During the Cenozoic period, Washington’s prehistoric seas began to move away. The new land became a majestic marshland, dotted with cypress, oak, elm, and ginkgo trees. Through lava flows and water, some of these forests were petrified and immortalized by time, having transformed into stone! Washington’s Ginkgo Petrified Forest State Park, for example, is renowned for its rare specimens of petrified ginkgo trees. It is known as one of the most ecologically unique fossil forests in North America. 

petrified wood or fossil wood

When trees fossilize over time they eventually turn into stone, and then we call it petrified wood.


Where to See Fossils in Washington

There may only be one dinosaur in Washington, but the state is home to many sites where you can find ancient fossils from many other creatures that roamed the area millions of years ago. Here is a list of some of the best places to see fossils in Washington!

Gingko Petrified Forest State Park

The 7,124-acre Ginkgo Petrified Forest State Park is truly special because there are more than 50 species of petrified wood found here! The park is also a registered National Natural Landmark due to its 27,000 feet of shoreline on Wanapum Lake along the Columbia River. It is a fantastic place to explore ancient fossils and see the stunning views of this area. You can learn more about petrified wood on the Trailside Museum and Trees of Stone Interpretive Trail with its 1.25 miles of trails weaving through petrified logs in their original setting, plus an additional 3 miles of hiking trails.

The park’s Wanapum Recreation Area also offers plenty of fun things to do, from campgrounds and boat ramps to a swim beach for days of fun in the sun. The Ginkgo Petrified Forest Interpretive Center is also a great place to visit and has day-use picnic areas and exterior displays. It offers incredible views of the Columbia River, Sentinel Gap, and the surrounding Ice Age flood-carved basalt landscape. Explore the geologic story of the Vantage Petrified Forest in the indoor exhibits for a fascinating look at one of North America’s most diverse petrified wood collections.

Log of petrified wood

There are more than 50 species of petrified wood found in Ginkgo Petrified Forest State Park.


Stonerose Interpretive Center & Eocene Fossil Site

Nestled in the northeastern part of the state, the Stonerose Interpretive Center & Eocene Fossil Site is a one-of-a-kind experience for the whole family. There was once an ancient lake covering this area, offering a fascinating insight into the geologic and biologic past of the Pacific Northwest. With fossil beds dating back to the Eocene period (50 million years ago!), there is plenty to explore. You can even dig for your own fossils — mostly leaf fossils, but occasionally insects and fish too! Though patience is required, your chances of making a discovery are excellent.

Burke Museum of Natural History and Culture

The Burke Museum of Natural History and Culture in Seattle, Washington, is a must-see for anyone interested in discovering more about the natural world. From its expansive fossil collections to its rotating culturally-driven exhibits, there’s something for everyone to explore. Its interactive displays make learning about history and science fun for children and adults alike. You can check out their online catalog to see what amazing fossils and artifacts they have!

Western Washington University

Located in Bellingham, Washington (in the northwest corner of the state near Canada), Western Washington University offers a variety of geological displays including rocks, fossils, and minerals. Be sure to explore the Environmental Sciences building to view the range of fossils from the Geology Department.

Sequim Museum & Arts Center

The Sequim Museum & Arts Center in Sequim, Washington (located on the Olympic Peninsula), showcases the fossilized bones of the Manis mastodon. Discovered in 1977 by Sequim resident Emanuel Manis along with a bone projectile point, this mastodon’s remains are accompanied by a variety of other objects. Visitors can also view local fossil mollusks on display at the museum.

The Granger Dinosaurs

Technically this last one doesn’t involve fossils, but if you want to see dinosaurs in Washington or are looking for a unique place to visit, then Granger, Washington, is a must! Visitors can marvel at over thirty dinosaur statues that were created by the people of Granger. The original project began in the 1990s with the purpose of revitalizing the Main Street and downtown area of Granger, but it has since become a wonderful spot for families on road trips. 

Today there are more than thirty dinosaur statues in Granger, including a plesiosaurus in the paddleboat pond, a spinosaurus near the freeway exit, an ankylosaurus family at Granger Hisey Park, a styrocosaurus outside of Granger City Hall, and a tyrannosaurus rex bursting out of the Public Works garage. Most of the dinosaurs are kid-friendly and encourage climbing. Even the public toilets in Granger are encased in an erupting volcano! 

Every year, Granger invites the public to join in on the fun during their Dino-N-A-Day, usually held on the first Saturday of June. People can get creative and take part in building their own unique dinosaur sculptures. It’s a great way to show your creativity and have some fun!

Where is Washington Located on a Map?

Washington, which is officially known as the State of Washington and commonly referred to as Washington State to differentiate it from the national capital, Washington, D.C., is a state situated in the Pacific Northwest area of the Western United States.

Here’s Washington on a map:

The photo featured at the top of this post is ©

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About the Author

Kellianne Matthews is a writer at A-Z Animals where her primary focus is on anthrozoology, conservation, human-animal relationships, and animal behavior. Kellianne has been writing and researching animals for over ten years and has decades of hands-on experience working with a variety of different animals. She holds a Master’s Degree from Brigham Young University, which she earned in 2017. A resident of Utah, Kellianne enjoys creating, exploring and learning new things, analyzing movies, caring for animals, and playing with her cats.

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