Ochotonids (pikas) are an ancient group of mammals originating in the Oligocene of Asia and flourishing in the Miocene of the Old World. During the Pliocene they reduced both their diversity and abundance, Only the Pleistocene genus Ochotona survived to the present. Their current geographic diversity is concentrated in Asia, where 28 species exist today. Outside of Asia, ochotonids are represented by one living species in Europe and two living species in North America. There were likely three main immigrations to North America since the Miocene: (1) at the beginning of the Miocene represented by the appearance of Oreolagus; (2) at the Miocene- Pliocene boundary represented by the appearance of Ochotona spanglei; and (3) during the Early Pleistocene with the appearance of Ochotona whartoni, and small pikas close to the "Ochotona pusilla group". Extant, endemic North American species appear in the Pleistocene.