Reptiles evolve many new species. Reptile fossils are abundant: aquatic reptiles, "stem reptiles," early ancestors of snakes and lizards, ancestors of turtles, and archosaurs are the first in line of the great ruling reptiles to come. The first mammal-like reptiles also appear.
Most paleontological excursions through time focus on large land animals. Ocean water, however, which is Earth's largest habitat, also bustles with life. As tectonic plates move and collide, altered land-masses, with their nutrient enriched coastal habitats, appear and disappear.