In taking on a 3D dinosaur cake (or any "standing" animal cake) there is a lot that goes into the cake design, before the cake is even baked! I read information online on how to create leg and neck support using PVC pipes and other items you can find at Home Depot. I didn't want to go that route...I wanted instead to achieve the look of a standing dinosaur in a more creative (and less constructive) way.
First, I started off with a wire hanger, saran wrap, duct tape and 2 pieces of foam board. I shaped the wire hanger into the "neck" of the dinosaur and then taped the base down onto the first piece of foam board. I took the second piece of foam board and cut it in half and glued each half on top of the wire hanger base to make one thick board, with a wire neck coming from the bottom.
(I wish I had a picture of that, but neglected to take one at this stage...)
Next, I tightly wrapped the wire hanger in saran wrap so that no part of the hanger would come in contact with the cake. I covered the foam board in green fondant.
Then I put my cakes (1 10"round on bottom, 2 9" round on top, already filled) right up against the hanger on the board and started carving to shape the dinosaur's back and legs. I used cereal treats to cover the wrapped hanger, making a long neck and head. Next I crumb coated it all in vanilla buttercream.
I used more cereal treats to create a tail and to give more depth to the legs. The birthday boy requested a buttercream iced cake (no fondant) but agreed for fondant facial features. I figured the best way to achieve a clean, realistic face was to use fondant for the skin, eyes and teeth. I shaped and added fondant pieces until I achieved this look...
Then I covered the dinosaur in different shades of blue buttercream and added a piece of black fondant under the belly to give a better appearance to the legs.
I kept playing with the icing and shading until I got the look I wanted. Next I added fondant rocks and bushes and trees to give the illusion that my dinosaur was standing on four legs. You can see my finished Brachiosaurus cake here.