Fossil models are created when you place a bio-fossil on the ground. They are entities.
Right-click on the ground while holding a Bio-fossil to create a Fossil Model. It randomly makes one dinosaur model from these kinds: Triceratops, Tyrannosaurus, Pterosaur, Plesiosaur, Mosasaurus, Stegosaurus, Brachiosaurus, Spinosaurus, Compsognathus, Deinonychus, Ankylosaurus, Liopleurodon, Allosaurus, Ceratosaurus and Gallimimus. It is possible to make them bigger by right-clicking them while holding bones. They can be demolished with a single hit, recovering the bio-fossil and all previously used bones.