Pteridophytes are known as the plant kingdom's Snakes because they are the first type of plants to be entirely terrestrial. In the animal kingdom, reptiles were the first animals to be completely terrestrials. It is by a similar logic that bryophytes are called amphibians of the plant kingdom. They are dependent on both land and water for survival and reproduction.Like the reptiles, pteridophytes are so widespread that they are the second most diverse subgroup of land plants following angiosperms. There are about 11000 species of pteridophytes in the world. Both Bryophytes and Pteridophytes have a lineage running back to four hundred million years, as suggested by fossil records. There is evidence suggesting that there existed treelike ferns as tall as 36.5 meters, known as Lepidodendron, an ancestor of modern club mosses.