As the spread of Mesozoic flora proceeded, so did development of animal life. Largely aquatic during the Paleozoic, Mesozoic fauna developed any number of land-based forms of a reptilian nature. The best known among them are known today as Dinosaurs. Based on The Record of the Rocks there were several classes of reptiles as follows: 1. * Theriomorpha 2. * Crocodile 3. * Plesiosaurs 4. * Ichthyosaurs 5. * Mosasaurs 6. * Dinosaurs And then there were the birds, with the earliest known variety being the Archaeopteryx.