Dinosaur fossil birthday cake - chocolate mousse cake, marshmallow fossils and chocolate dirt
Cakes & biscuits,  Dinosaurs,  Yum

Dinosaur fossil birthday cake

When Miss M decided that she wanted a dinosaur theme for her birthday party, I knew the birthday cake had to be special. I was short on time, so it needed to be simple and quick, yet delicious and dino-themed. The result was this dinosaur fossil birthday cake. Here’s how to make one for your own little dinosaur aficionado.

The lacklustre dinosaur birthday cake inspiration

I browsed Pinterest for ideas for dinosaur-themed birthday cakes but was not inspired.

I could frost cupcakes in an appropriate dinosaur colour and lay them out in the shape of a dinosaur. Not only was the idea a little boring, but I was sure that Miss M would want pink cupcakes. How do you make pink cupcakes look like a dinosaur?

I thought about making a Stegosaurus shaped cake with green (or pink or purple) frosting and nacho chips or square biscuits for the plates on the back. Some that I found look quite cute. However, allergies of some of our party guests mean this would not work.

I considered using toy dinosaurs as decoration. We only have a few small dinosaurs and we did not have enough time to buy more. Miss M’s favourite dinosaur is currently the Brachiosaurus. Our 25cm tall toy Brachiosaurus would have resulted in a very flat, squashed cake. The paper mâché Brachiosaurus would not have been very hygienic on top of the cake, either.

A colourful cake with fondant dinosaurs was also not an option. Obviously, I had neither time nor patience for such a cake. Allergies might have nixed this idea, but it did not matter. I was too late to order one, anyway.

One problem solved

I decided to make my allergy-friendly chocolate cupcakes and turn them into dinosaur nests. One easy dinosaur-themed birthday cake – or cupcakes. This meant that I did not have to worry about allergies when deciding on the birthday cake.

I changed the frosting tip to make it more squiggly and nest like and added little foil eggs. The dinosaurs had not laid eggs in all the nests (because some didn’t use nests, obviously and scientifically).

Problem two solved

As the kids would have cupcakes to eat, the birthday cake needed to be something that the adults would enjoy. My decadent chocolate mousse cake fit the bill perfectly. Still, there was the question of how to decorate it to fit the dinosaur theme.

Of course, you don’t have to use the chocolate mousse cake as your base for this dinosaur fossil birthday cake. Any cake, preferably chocolate, will work. It does not matter whether it is store-bought, a packet mix or your Grandma’s Texas sheet cake recipe. Just cover it with chocolate cream or frosting to look like ‘dirt’.

Problem three solved: a dinosaur fossil birthday cake

The solution ticked all the boxes:

  • The decorations are light (so they won’t sink into the cake like plastic dinosaurs)
  • It is super easy
  • It doesn’t take much time to execute
  • It does not have to be exact to look the part
  • There are no additional cake toppers, banners etc to make
  • It is definitely on-theme
  • It does not matter if the little dinosaur aficionado prefers pink or green dinos, and
  • I could decide what cake base to use

I also didn’t need to purchase many additional ingredients as I already had marshmallows. At the same time, the idea was simple enough that the kids would recognise the fossils and the adults and kids would not be turned off by strange ingredients (such as excessive fondant or nacho chips).

Do you need a dinosaur-themed birthday cake?

If you are planning a birthday party for your own little dinosaur aficionado, whether boy or girl, make this dinosaur fossil birthday cake. It is easy, on-theme and does not take much time to execute – your little dinosaur aficionado/birthday boy or girl can even help. It is also not your typical dinosaur-themed birthday cake.

More importantly, this themed cake lets you use whatever cake you like as a base – whether it is a store-bought base, a packet mix or a lovingly-made decadent chocolate mousse cake. Save on time, stress and have a dinosaur fossil birthday cake that still tastes good and fits the theme.

Dinosaur fossil birthday cake banner
Dinosaur fossil cake

Prep Time: 20 minutes

20 minutes

Birthday cakes (Dinosaur party)


Servings: 10 slices

Dinosaur fossil birthday cake

The best (and most original) birthday cake for a rainbow dinosaur birthday party: a dinosaur fossil cake! While a little fiddly, it is actually quite easy and is guaranteed to delight your little dinosaur aficionado.


  • Cake of your choice to use as a base.
  • If necessary: chocolate cream or frosting
  • Large (white) marshmallows
  • Chocolate ‘dirt’.


  1. If the cake is not already frosted, frost the cake so that the top is covered in the chocolate frosting or cream.
  2. Use a sharp knife to cut the marshmallows to form dinosaur bones. You will need leg bones, backbones, tail bones, ribs and skull and jawbone at least. Ours was a carnivore, so I added arms and hands and teeth.
  3. Place them on the cake so that the dinosaur is recognisable, but not necessarily anatomically correct – it is a fossil.
  4. Sprinkle the chocolate ‘dirt’ around the marshmallow fossil to give the impression of dirt and rocks.


I used baby chocolate buds for the dirt because that was the best thing I could find. If you have chocolate shavings, or a broken up flake bar or a crushed Hershey’s Krackel bar would work. Chocolate sprinkles would work if that is the best thing that you can find.

Use a sharp knife. The marshmallows will probably stick to the knife (and this will get worse with each additional marshmallow): be patient.

Your dinosaur fossil does not have to be anatomically correct!

Enjoy sign-off
Dinosaur fossil birthday cake: chocolate mousse cake with marshmallow fossils and chocolate dirt. An easy dinosaur-themed birthday cake for your little dinosaur aficionado

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