Abstract
This article provides an overview of how differences in brain organization of tetrapods might have evolved and how they can be recognized. The current views of reptilian taxonomy, with special emphasis on the relationship of turtles to other reptiles are reviewed. Reptilian sensory systems and regions are then described and compared with those of amphibians, birds, and mammals, noting features that have been especially divergent. Transitions from an amphibian-like state and to avian- and mammalian-like states are discussed.