Currently the order Lagomorpha contains two families and 13 genera. There was a third family up until the early 1800s, but it is now extinct. Lagomorphs include pikas, hares, and rabbits.
Lagomorphs live throughout Europe, Asia, Africa, North America, and the Northern areas of South America. Humans have also introduced them to many islands where they did not originally live. They are small mammals that are closely related to the rodents (order Rodentia); in fact they were included as a superfamily of Rodentia until the early 1900s. They are distinct from the rodents in that:
- They have four incisors in their upper jaw (two big ones, with two small peg-like ones hiding behind them), while rodents have only two.
- Their incisors are fully enameled, while rodents' teeth are only enameled on the front and sides.
- They are herbivores, while rodents are omnivores.
- They need to re-ingest their own droppings in order to completely digest the nutrients from the cellulose in their diet. Rodents supplement their diets with meat, and so do not have this problem.
- The males do not have a baculum (penis bone), while rodents do.
- The male's scrotum is in front of the penis. (Just like the marsupials!)
- Their skulls tend to be more porous than those of rodents.
- Lagomorphs have very short tails, while rodents usually have longer tails.
Like rodents, their incisors grow throughout their life, requiring constant gnawing in order to wear them down. Both groups lack canines, and have accordingly large diastemas. Both rodents and lagomorphs have folds of skin in their lips (or sometimes in the cheeks, in the rodents) that can be drawn into the diastima, behind the incisors, so that they can gnaw with their mouth closed. Like many rodents, lagomorphs can close their nostrils.
Taxonomy comes from Animaldiversity, except for Prolagidae, which is from Wikipedia.