Dinosaur Fossil Molds and Casts

Fossils molds and casts are often what we see & touch in museums. In this STEM project YOU will make your own!


Play doh

Dinosaur Skeleton Toy, Plants

Elmers Glue


What is a Fossil and How is it Made?!

A FOSSIL is formed when plants or animals are quickly buried under sediment (particles carried by wind or water that over time, cover the surface of the land and are consolidated into rock). Fossils form over thousands of years, and then are carefully uncovered by paleontologists! 

FOSSIL MOLDS are created when the sediment hardens, and the dinosaur bones fully disintegrate, leaving open spaces where the bones once were. When Fossil molds are found, they can be filled and used to make many copies of the fossil!

FOSSIL CASTS are found when a fossil mold underground is filled with sediment to form a fossil in the actual shape of the animal bones! Instead of being made of actual bone, fossil casts are made of hardened sediment (rock!)

Roll Up Your Sleeves, Paleontologists!

Now that you know all about Fossils and how they’re made, it’s time to make your own!

1. Take your Play Doh and shape it into a thin round disk, about 1cm thick. You want the diameter to be big enough to fit the length of your dinosaur skeleton toy. 

2. Push your dinosaur gently into your Play Doh to create a Fossil Mold! Make sure not to go all the way through.

3. Now it’s time to create a Cast from your Fossil Mold! 

4. Pour your glue into the Fossil Mold and let it sit for 24-48 hours. 

5. When dry, carefully remove your cast from the Play Doh to reveal your creation! 

(Our blue fossil mold had a tiny hole in the bottom, so we had a hollow spot in our dinosaur cast as well)

We noticed that just like real fossils, our red fossils ended up in two pieces. Talk about how paleontologists sometimes have to put together a puzzle of fossils to find a complete dinosaur!

We also loved matching up the fossil casts with the dinosaur they were made from. Notice how the fossils don’t look exactly like their skeleton. What is the same? What is different? Fossils can give us a really good idea of what dinosaur life was like, but they aren’t a perfect picture!


Enjoy watching your little one explore their new fossils! We can’t wait to see how your fossils turn out! Make sure to share your paleontology successes with us on social media! 

Extend Your Play!