The Order Perissodactyla comprises the odd-toed ungulates, hoofed mammals with an uneven number of toes on their hind feet. This order includes horses, zebras, rhinoceroses, and tapirs. Perissodactyls are primarily herbivorous, feeding on grasses, leaves, and shoots, and have a large, simple stomach or hindgut fermentation system to digest fibrous plant material. They are generally large, terrestrial animals with strong limbs adapted for running or supporting heavy bodies. Ecologically, they play important roles in shaping vegetation and maintaining grassland and forest ecosystems.