Prolagus

Prolagus was first named by Auguste Pomel in 1853. Prolagus has been considered by most taxonomists to be a member of the pika family Ochotonidae, but distinct from living pikas, which all belong to the genus Ochotona.^[5] Erbaleva in 1988 suggested it represented the only member of the monotypic family Prolagidae due to its distinct dental formula;^[6] this proposal was considered invalid by Nieves López Martínez, due to the fact that many mammal families have lineages with distinct dental formulae.^[5] However, many authorities such as the IUCN Red List and American Society of Mammalogists accept Prolagidae as valid.^[7][8] Analysis of a partial mitochondrial genome of Prolagus sardus suggests that it is more closely related to Ochotona than to Leporidae (which contains rabbits and hares), with an estimated divergence between Prolagus and Ochotona about 30 million years ago.^[9]

Prolagus is distinguished by a continuously growing dentition, a lack of a lower third molar, a trilobed second lower molar and unusually shaped premolars, with additional cusps in the lower third premolar. In comparison to modern pikas of the genus Ochotona, they have one less dorsal vertebra in the spinal column. Most species of Prolagus probably weighed around 500 grams (1.1 lb), similar to a living pika.^[5] A specimen with preserved soft-tissue is known from late Miocene aged deposits from Andance in France, which shows that its overall proportions, shape of the ears and lack of tail are similar to living Ochotona.^[5]

Over 20 species of Prolagus have been named.^[5][10][11]

Prolagus likely evolved from the Oligocene-earliest Miocene genus Piezodus. The distribution of Prolagus between 20-8 million years ago extends from the Iberian Peninsula in the west to Anatolia in the east, extending as far north as central Germany, though it was absent from the Italian Peninsula. Early Prolagus species are thought to have inhabited subtropical swamp and wetland environments, with a similar ecology to the living marsh rabbit (Sylvilagus palustris). In many European Miocene localities remains of Prolagus are extraordinarily abundant, and Prolagus species probably played a key role as prey for many predators. During the late Miocene, Prolagus dispersed into North Africa due to the connection between Africa and Europe as a result of the Messinian salinity crisis. The range of Prolagus shifted southwards and substantially contracted outside of North Africa during the Pliocene, due to climatic cooling and increasing aridity, though the genus reached its highest species richness at 9 species due to habitat fragmentation leading to speciation.^[5] Prolagus first arrived in Corsica, Sardinia, and other Mediterranean islands at the early-late Pliocene boundary, likely due to an emergent land connection. The earliest remains of Prolagus on the islands are represented by the species P. figaro, ancestral to P. sardus.^[17] Among the last continental species of Prolagus is P. calpensis from the Early-Middle Pleistocene of the Iberian Peninsula. By the beginning of the Late Pleistocene, Prolagus was confined to the single species P. sardus on Corsica, Sardinia and surrounding islands. While decline of the distribution Prolagus on the mainland of the continents was primarily driven by climatic change, the cause of the final extinction of the mainland Prolagus species is unclear, but one factor suggested is increased predation pressure.^[5] The Sardinian pika probably became extinct sometime between 393 BC (the timing of the last reliable radiocarbon date) and the 6th century AD, likely due to introductions of invasive species by humans.^[18]