Simple, fun and dino-licious: 3 steps to make a dinosaur fossil birthday cake

Are you looking for a simple but fun dinosaur birthday cake for a dinosaur-themed birthday party? This dinosaur fossil birthday cake has only 3 steps and 3 key ingredients but lots of character. And you definitely don’t need to be a master pastry chef to make it!

“What is it, Mummy?”

My first attempt at a dinosaur birthday cake was a complete and utter failure. Our LDA has a good imagination. Normally.

I’ve since discovered a much easier way.

Our dinosaur fossil birthday cake is simple, unexpected and fun. And fortunately, dinofication only takes three steps.

Rexy's recipe roundup icon: watercolour T-Rex with a watercolour heart

Rex’s recipe rundown

TITLE: Dinosaur fossil birthday cake
CRAFT: Birthday cake with dinosaur fossil decoration
DINOSAUR: Any you can create as a fossil using marshmallows
BEST FOR: Birthday parties!
EASE: 5 out of 5 – just watch out for sticky marshmallows

Some of the links below are affiliate links. We may earn a small commission if you use these links to make a purchase. Thank you! Please read our full disclosure for more information. 

Dinosaur fossil birthday cake, with a chocolate mousse cake base and chocolate chip rocks

Why you want to make this dinosaur fossil birthday cake

When you’re planning your dinosaur birthday party, you need a dinosaur birthday cake. This dinosaur fossil birthday cake is easy and quick to make with 3 steps and a few key ingredients. And you do not need to be a master pastry chef to make it.

I made it for a combined 50th and 7th birthday party. D-Rex is now a fossil; luckily, our LDA is enamoured of them! I used a chocolate mousse cake as a base. This made it delicious, simple and suitable for both “age” groups.

As a bonus: you can make it as large or small as you need it to be. We (and all chocoholics) prefer chocolate cake, but it can be any flavour you wish.

3 simple steps

1. Start with a cake

Use any cake you like, whether store-bought or homemade. Cover the top with chocolate (or at least brown) frosting. You can choose whether to cover the sides as well or go for the naked cake look. Don’t use glaze as your fossils won’t stick to your cake.

I used this chocolate mousse cake. I even cheated and used packet mix for the chocolate mousse (good quality of course).

Simple dinosaur birthday cake, with marshmallow fossil and chocolate dirt

2. Add your fossil

White marshmallows are your friend. Cut and stretch them to form the bones of your fossil and lay them out on the top of your dinosaur fossil birthday cake.

The marshmallows will stick to your fingers. You can rub them in a bit of corn starch, which will help a little (but not much).

The beauty of using marshmallows is you don’t have to buy a(nother) dinosaur fossil mould to make the fossil for the dinosaur fossil birthday cake.

Remember: Your fossil does not need to be perfect. Most dinosaur remains discovered are missing bones (Sue, the most complete T-Rex fossil ever found is 90% complete by bulk (73% by elements)). Over time, bones shift and are often not laid out as they would be in the original animal.

Get our free
Dinosaur party Printables

When you join our newsletter


3. Add stones and dirt

Make the top of the cake look like rocks and dirt surrounding the fossil.

We used mini chocolate cookies and chocolate shavings (they came pre-shaved). You could use:

Use them to cover the rest of the frosting, leaving the marshmallow “fossils” free.

Dinosaur fossil birthday cake, with marshmallow therapod fossil

Optional additions

If you want, you can add some tools or other paraphernalia to make your dinosaur fossil birthday cake look more like a fossil dig site. These could be out of plastic. We found these toys useful for dinosaur dig-related tools:

You could also make some tools out of fondant. Or buy some plastic shovel spoons for guests to use to eat your cake.

If you feel inspired, add some grid lines. Palaeontologists use these to map out where they find each fossil at a site. Toothpicks and some string or thread work well.

Of course, make sure to leave some space for your candles!

Don’t want a dinosaur fossil birthday cake?

This dinosaur fossil birthday cake idea is simple and versatile. Like the Europasaurus, anything you can do in large can be made in small, too.

Make a smaller version! These decorations work for cupcakes too.

Fossil dig cups:
Make chocolate mousse, divide it between some cups or jars, and add a marshmallow fossil or two and some chocolate dirt.

Prehistoric tar pits:
Don’t have mousse? Use pudding or custard and partially submerge your marshmallow bones. Voilà!

Can I make this dinosaur fossil birthday cake vegan?

Of course!

Use your favourite vegan cake recipe to make your base and cover it with your favourite vegan chocolate frosting.

Marshmallows contain gelatin, which is normally not vegan. However, various vegan marshmallows are available on the market and will work perfectly for this recipe.

Use some vegan “chocolate” covered nuts and chocolate chips and add liberal amounts of shaved vegan chocolate.

Simple dinosaur fossil birthday cake with a stylised dinosaur fossil made out of marshmallows

Can I make this cake in advance?

Yes, but not too far in advance.

The cut marshmallows will dry out the longer they are left exposed to the air. You could make the cake the night before, but I would not make it much earlier.

Store the cake somewhere cool, not in direct sunlight to prevent the chocolate from melting. If you store it in the fridge, make sure to cover it: the marshmallows will absorb any funky smells from your fridge.

Make this simple dinosaur fossil birthday cake for your next dinosaur birthday party

The crowning jewel for any dinosaur birthday party has to be the dinosaur birthday cake. With just three steps and three key ingredients, this simple and fun dinosaur fossil birthday cake is bound to be a hit with roaring party guests and bakers alike.

And your little dinosaur fan will not need much imagination to know what it is.

What type of dinosaur birthday cake will you be making for your next dinosaur birthday party?

RAWR! Enjoy the party, Mamasaurus sign-off with pink cupcake with a green Stegosaurus on top

Dinosaur fossil birthday cake

Yield: 12 pieces
Prep Time: 20 minutes
Total Time: 20 minutes

A fun way to decorate a dinosaur birthday cake that's quick and easy to implement, cheap, looks spectacular and is definitely on theme for your dinosaur birthday party.


  • 1 cake of your choice
  • Chocolate frosting (enough to cover the top of the cake)
  • About 10 large marshmallows
  • Milk or dark chocolate-covered nuts, raisins or malt balls
  • Milk or dark chocolate shavings or sprinkles


  1. Frost the top of the cake with the chocolate frosting.
  2. Cut the marshmallows into shapes resembling dinosaur bones and lay them out on the top of your frosted cake to vaguely resemble a dinosaur fossil.
  3. Sprinkle your chocolate-covered nuts and chocolate shavings around the marshmallow fossil to create the rocks and dirt that it is embedded in.


If you use a chocolate mousse cake, you won't need the frosting.

Feel free to add additional dig site tools (either borrow some toys or make some out of fondant) to complete the look.

Nutrition Information
Yield 12 Serving Size 1
Amount Per Serving Calories 144Total Fat 6gSaturated Fat 2gTrans Fat 0gUnsaturated Fat 3gCholesterol 9mgSodium 56mgCarbohydrates 21gFiber 1gSugar 16gProtein 3g

Nutrition information is a guide only as it will depend on the specific products and brands you choose to use for this recipe.

Did you make this recipe with your little dinosaur fan?

Share it on Instragram and tag @mrsmaiasaura to let us and other dinosaur fans know!

Save for later

Pin: The simplest dinosaur birthday cake: Just 3 steps, with an image of the cake with the fossil/marshmallow dinosaur and some bunting on a white background

Sharing is caring!

Similar Posts

Leave a Reply

Your email address will not be published. Required fields are marked *