The Origin of the P 3 Pattern of Sylvilagus, Caprolagus, Oryctolagus and Lepus

An Upper Pliocene population of Nekrolagus progressus (Hibbard) represented by 178 P3s from the Rexroad fauna has 11.8% of the individuals with a P3 enamel pattern that is like the Ps pattern of Sylvilagus, Caprolagus, Oryctolagus and Lepus. For the first time in the fossil record there is evidence for the time and place of the variation (mutation) within a population that produced a character of generic grade. It is proposed that this pattern developed in North America and gave rise to that now found in Sylvilagus, Caprolagus, Oryctolagus and Lepus. Cenozoic faunas of Eurasia that contain remains of Oryctolagus and Lepus are younger than the Rexroad fauna. Over 2,000 Recent Lepus, Oryctolagus and Sylvilagus dentitions were examined. Twelve Recent specimens of these three genera were found that contained the Nekrolagus pattern. The genera are quite recent in origin. These rabbits provide an excellent group for comparative study with the late Pliocene Nekrolagus to establish the rate of generic development. A phylogenetic summary is given to show the relationship of the Leporinae as based upon the development of P2 and P3.