Order Perisodactyla is a once ubiquitous ungulate characterized by an odd-number of hooved toes. Equidae (horses) possesses a one-hooved-toe. The closely related Tapiridae (tapirs) and Rhinoceratidae (rhinoceroses) feature a three-hooved- toe. Perisodactyla is currently limited in their distribution and variety. However, fossil studies have revealed that they were once quite prosperous.