Rodents show less variation in body plan than many other mamillian orders. Most are squat, compact mammals with short limbs and a tail. There are a few large species, mostly in South America. The larger species have evolved long legs and a larger body fit for a niche in the grassy planes area where there is little competition by other large herbivores. One highly variable feture between rodents arises in the tail structure.
All rodents have razor-sharp insisorts that can gnaw through anything.
The name rodent comes from the Latin word rodere, which means to knaw . Molars are often covered with many laters of convoluted enamal. They are ground down by the opposite number on the other jaw. If the incisors become misaligned the teeeth will grow around an pierce the skull. Rodents have between 12 and 22 teeth depending of the species except for the silvery-mole rat which has 28 teeth.