Pentalagus furnessi

DIAGNOSIS. Relative to other leporids, rostrum of Pentalagus furnessi (Fig. 1) is shorter and heavier and posterior projection of superorbital process is well developed, heavier, and more blunt (Fig. 2; Lyon 1904). Incisive foramina are narrow, their sides approximately parallel, resembling in shape those in Pronolagus, but very much smaller. Audital bullae are very small, more reduced in size than in Pronolagus. P2 of Pentalagus has 3 grooves compared with 2 grooves in Brachylagus idahoensis, Nesolagus netscheri, and Romerolagus diazi. Unlike Romerolagus diazi, the anterior reentrant angle is present in P. furnessi. The anterointernal reentrant angle is present in P. furnessi but absent in Lepus, Oryctolagus, and Sylvilagus. Only Pentalagus has all 5 reentrant angles and the most complicated enamel crenulation in the Leporidae (Dawson 1958; Hibbard 1963; Tomida and Jin 2002).