An introductory presentation for my high school Zoology Course that examines the Class Reptilia.

2. Class Reptilia Phylum Chordata

25. Only one species of gavial (or gharial): Gavialis gangeticus

28. Four Legs and A Third Eye? It's pretty common knowledge that vertebrate animals have two eyes, but this was not always the case. Our earliest fish-like ancestors, evolved with a third hole in their skulls and an eye that connected directly to the brain called the pineal eye. It appears that this adaptation became converted over time to a small organ associated with the control of hormone production — the pineal body or gland. But in tadpoles, other amphibians, and some of the lizards, among them the Tuatara , a living relic lizard of the Sphenodont group, a third centrally located eye has remained although the function is not fully understood. It is sensitive to changes in light and dark, but it does not form images, having only a rudimentary retina and lens. It is visible as an opalescent gray spot on the top of the animal's head. Also, some snakes have an "extra" pair of "eyes" (more correctly, sensory organs) located on the forehead that can detect infrared radiation. They can "see" the heat of a mouse from a meter away, even in conditions where our eyes would see only pitch dark.