Lagomorph

The lagomorphs are the members of the taxonomic order Lagomorpha, of which there are two living families: the Leporidae (hares and rabbits) and the Ochotonidae (pikas). The name of the order is derived from the Greek lagos (λαγος, "hare") and morphē (μορφή, "form").

Though these mammals can resemble rodents (order Rodentia) and were classified as a superfamily in that order until the early twentieth century, they have since been considered a separate order. For a time it was common to consider the lagomorphs only distant relatives of the rodents, to whom they merely bore a superficial resemblance.

The evolutionary history of the lagomorphs is still not well understood. Until recently, it was generally agreed that Eurymylus, which lived in eastern Asia and dates back to the late Paleocene or early Eocene, was an ancestor of the lagomorphs. More recent examination of the fossil evidence suggests that lagomorphs may have instead descended from Anagaloidea also known as mimotonids, while Eurymylus was more closely related to rodents (although not a direct ancestor.) The leporids first appeared in the late Eocene and rapidly spread throughout the northern hemisphere; they show a trend towards increasingly long hind limbs as the modern leaping gait developed. The pikas appeared somewhat later in the Oligocene of eastern Asia.

Characteristics
Lagomorphs differ from rodents in that:
 * they have four incisors in the upper jaw (not two, as in the Rodentia);
 * they are almost strictly herbivorous (unlike rodents, many of which will eat both meat and vegetation);

However, they resemble rodents in that their teeth grow throughout their life, thus necessitating constant chewing to keep them from growing too long.

Classification

 * Order Lagomorpha Brandt 1885
 * Family Leporidae Fischer de Waldheim 1817 (rabbits and hares)
 * Subfamily † Archaeolaginae
 * Genus †Archaeolagus Dice 1917
 * Genus †Hypolagus Dice 1917
 * Genus †Notolagus Wilson 1938
 * Genus †Panolax Cope 1874
 * Subfamily Leporinae Trouessart 1880
 * Genus †Alilepus Dice 1931
 * Genus Brachylagus
 * Genus Bunolagus
 * Genus Caprolagus Blyth 1845
 * Genus Lepus Linnaeus 1758
 * Genus Nesolagus Forsyth Major 1899
 * Genus Oryctolagus Lilljeborg 1874
 * Genus †Nuralagus Lilljeborg 1874
 * Genus Pentalagus Lyon 1904
 * Genus †Pliolagus Kormos 1934
 * Genus †Pliosiwalagus Patnaik 2001
 * Genus Poelagus
 * Genus †Pratilepus Hibbard 1939
 * Genus Pronolagus Lyon 1904
 * Genus Romerolagus Merriam 1896
 * Genus †Serengetilagus Dietrich 1941
 * Genus Sylvilagus Gray 1867
 * Subfamily †Palaeolaginae Dice 1929
 * Tribe †Dasyporcina Gray 1825
 * Genus †Coelogenys Illiger 1811
 * Genus †Agispelagus Argyropulo 1939
 * Genus †Aluralagus Downey 1968
 * Genus †Austrolagomys Stromer 1926
 * Genus †Aztlanolagus Russell & Harris 1986
 * Genus †Chadrolagus Gawne 1978
 * Genus †Gobiolagus Burke 1941
 * Genus †Lagotherium Pictet 1853
 * Genus †Lepoides White 1988
 * Genus †Nekrolagus Hibbard 1939
 * Genus †Ordolagus de Muizon 1977
 * Genus †Paranotolagus Miller & Carranza-Castaneda 1982
 * Genus †Pewelagus White 1984
 * Genus †Pliopentalagus Gureev & Konkova 1964
 * Genus †Pronotolagus White 1991
 * Genus †Tachylagus Storer 1992
 * Genus †Trischizolagus Radulesco & Samson 1967
 * Genus †Veterilepus Radulesco & Samson 1967
 * Tribe incertae sedis
 * Genus †Litolagus Dawson 1958
 * Genus †Megalagus Walker 1931
 * Genus †Mytonolagus Burke 1934
 * Genus †Palaeolagus Leidy 1856
 * Family Ochotonidae Thomas 1897 pikas
 * Genus †Alloptox Dawson 1961
 * Genus †Amphilagus Tobien 1974
 * Genus †Bellatona Dawson 1961
 * Genus †Cuyamalagus Hutchison & Lindsay 1974
 * Genus †Desmatolagus Matthew & Granger 1923
 * Genus †Gripholagomys Green 1972
 * Genus †Hesperolagomys Clark et al. 1964
 * Genus †Kenyalagomys MacInnes 1953
 * Genus †Lagopsis Schlosser 1894
 * Genus Ochotona Link 1795
 * Genus †Ochotonoides Teilhard de Jardin & Young 1931
 * Genus †Ochotonoma Sen 1998
 * Genus †Oklahomalagus Dalquest et al. 1996
 * Genus †Oreolagus Dice 1917
 * Genus †Piezodus Viret 1929
 * Genus †Russellagus Storer 1970
 * Genus †Sinolagomys Bohlin 1937
 * Genus †Titanomys von Meyer 1843
 * Family †Prolagidae Gureev, 1962 (Sardinian Pika and other related extinct pika-like lagomorphs)
 * Genus †Prolagus Pomel 1853
 * Family incertae sedis
 * Genus †Eurolagus Lopez Martinez 1977
 * Genus †Hsiuannania Xu 1976
 * Genus †Hypsimylus Zhai 1977
 * Genus †Lushilagus Li 1965
 * Genus †Shamolagus Burke 1941