Mastodons (nipple and tooth) were large, tusked, mammal species of the extinct genus Mammut, which inhabited Asia, Africa, Europe, North America and Central America from the Oligocene through Pleistocene epochs. The genus gives its name to the family Mammutidae, assigned to the order Proboscidea. They superficially resemble members of the proboscidean family Elephantidae, including mammoths; however, mastodons were browsers, while mammoths were grazers. This animal appeared during Cenozoic era, the most recent era of geologic time, from about 65 million years ago to the present. The Cenozoic Era is characterized by the formation of modern continents and the diversification of mammals and plants. Grasses also evolved during the Cenozoic. The climate was warm and tropical toward the beginning of the era and cooled significantly in the second half, leading to several ice ages. Humans first appeared near the end of this era.