For animals, the concept of Ultimate Perfection lies in a stage of existence that is unforeseeable: a being that no longer needs to adapt. Evolution is an ever-changing process unique to each species it affects, and while it is very gradual, happening often over hundreds of years, we can look back to find the main stages of a species' evolution to pinpoint the times at which the original species faded away and became a new one. While it is important to note that all species are in a constant state of evolution at all times, the best example of the movement to attain Ultimate Perfection from an animal's position is through evolution to become the most well-developed animal: a race to become better habituated in an ever-shifting environment. Animal's Ultimate Perfection explores the split between classes: for example, the evolution that lead to the split between reptiles and mammals. Mammals were evolved from a type of reptile (the original class of all animals) called synapsids. An early example of a synapsid is the Dimetrodon grandiswhich were reptile-like mammals, so-called due to being classified as a species from which the descendants evolved through a reptile-to-mammal evolution into "full" mammals. "Full" mammals implies the emergence of a single jawbone (as opposed to a reptile's many bones in the jaw), teeth that are differentiated for separate tasks (such as meat shearing rather than the fairly uniform grinding of plant matter) and the shift from widespread legs to legs directly beneath the body. True reptiles evolved after the Permian extinction into archosauromorphs, which are characterized by longer hind legs, whereas the mammals that survived this period often have shorter hind legs.