This new treatise is comprised of 24 papers covering virtually every recent development regarding fossil horses, rhinos, tapirs, and their extinct relatives. It includes materials currently available in no other reference, such as information on the oldest known rhino and the oldest known perissodactyl, as well as papers debunking myths about the evolution of horses, and strong evidence that hyraxes are not related to elephants. The summary chapter includes useful charts which show the relationships of all perissodactyl genera, their distribution in time and space, and a new classification of the order.