Pikas, hares, and rabbits (Lagomorpha)

Abstract

Abstract The pikas, hares, and rabbits (Fig. 1) are united into the monophyletic Order Lagomorpha based on the presence of a second peg-like upper incisor and foot morphology showing a unique calcaneal canal running diagonally through the lagomorph calcaneus (1). Based on the latter observation, which is also present in lagomorph fossils, it has been proposed that the order has had a long evolutionary separation from other related mammalian orders such as the Rodentia (1–3). The Lagomorpha currently comprises two extant families, the Ochotonidae (pikas, 30 species and one genus) and Leporidae (rabbits and hares, 60 species and 11 genera) (4). themonotypic pikas have a northern hemisphere distribution with most taxa conAned to Asia, where the upliJing of the Tibet Plateau probably played a major role in the diversification of taxa (5). the11 genera of rabbits and hares have a nearly global distribution (Holarctic, Ethiopian excluding Madagascar, northern Neotropical and Oriental) and their diversification is more than likely due to a series of dispersal and vicariance events that could be correlated to the formation and disappearances of intercontinental landbridges (6). From a paleontological perspective, evidence suggests either an Asian or North American origin for the order, but the pinpointing of the exact location is hampered by a scattered fossil record for the early and middle Eocene (7). It has been postulated that the Arst expansion of Leporidae occurred in North America during the Miocene (7), a notion supported by at least two recent fossil discoveries (8, 9), whereas the Ochotonidae probably originated in Asia. Here I review the available information on the timing of the Ochotonidae and Leporidae divergence.