Pictured left: Black rhinos (Diceros bicornis). Mila Zinkova, Wikipedia Creative Commons
Rhinocerotoidea: Rhinos are a very diverse group of perissodactyls that are easily identified by their molars, which have three crests their grinding surfaces that form a shape like the Greek letter Pi (π). The five species of living rhinos are all members of the family Rhinocerotidae, although they are a poor remnant of the great diversity of rhinos that once existed. Animals commonly referred to as rhinos form part of a much larger group known as the Rhinocerotoidea. Within this very large superfamily are three separate families: the Amynodontidae, Hyracodontidae, and Rhinocerotidae (true rhinos).