Megaherbivores (Greek μέγας megas "large" and Latin herbivora "herbivore") are large herbivores that can exceed 1,000 kg (2,200 lb) in weight. The earliest herbivores to reach such sizes like the pareiasaurs appeared in the Permian period. During most of the Mesozoic, the megaherbivore niche was largely dominated by dinosaurs up until their extinction during the Cretaceous–Paleogene extinction event. After this period, small mammalian species evolved into large herbivores in the Paleogene. As part of the Late Pleistocene megafauna extinctions, 80% of megaherbivore species became extinct, with megaherbivores becoming entirely extinct in Europe, Australia and the Americas. Recent megaherbivores include elephants, rhinos, hippos, and giraffes. There are nine extant species of terrestrial megaherbivores living in Africa and Asia. The African bush elephant is the largest extant species.
Extant megaherbivores are keystone species in their environment. They defoliate the landscape and spread a greater number of seeds than other frugivores. Extant megaherbivores, like most large mammals, are K-selected species and are characterized by their large size, relative immunity to predation, their effect on plant species, and their dietary tolerance.
