Wood isn't the only thing that can be petrified. These phytosaur bones from Petrified Forest are all that remain of a phytosaur that died and was buried in silt before it was eaten by a Metoposaur or it started to decompose. Phytosaurs fossils are by far the most numerous vertebrates (animals with a bony backbone) found at Petrified Forest. Phytosaurs were primitive members of the ruling class of animals at that time, the Reptiles, including the dinosaurs and their ancestors.