Fossil models are created when you place a bio-fossil on the ground. They are entities.
Use
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, and Liopleurodon. 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.
Using these fossils, you can glitch-duplicate bio-fossils. Constantly click both mouse buttons when holding a bio-fossil, so you will place and break these. Before you know it, you will have duplicated bio-fossils (works on build 6.0).