Brachylagus idahoensis (Merriam, 1891)

Christopher, Jass, N., Usa, J. J. & Usa, 2009, Pleistocene lagomorphs from Cathedral Cave, Nevada, PaleoBios 29 (1), pp. 1-12 : 4

Brachylagus idahoensis (Merriam, 1891)

Referred Specimens —See Appendix 1.

Description — Three specimens of Brachylagus idahoensis were identified from Cathedral Cave ( Fig. 4c). Two of the specimens retain simple anteroexternal reentrants and the trigonid and talonid are either completely (TMM 43693-1777), or nearly (TMM 43693-1776), separated by cementum. The extension of the anteroexternal folds across the tooth is characteristic of B. idahoensis ( Ramos 1999b) . Length and width of the p3s were: (TMM 43693-1777) - l = 1.8 mm, w = 1.6 mm; (43693-1776) - l = 1.8 mm, w = 1.8 mm.

A third p 3 specimen (TMM 43693-1775) with a damaged occlusal surface that was also identified as Brachylagus idahoensis is unique. In ventral view, it has a posteroexternal reentrant that extends across two-thirds of the tooth, but exhibits an enamel lake in the position of a posterointernal reentrant. Because the joining of the posteroexternal reentrant with the enamel lake would result in a morphology more similar to B. idahoensis than B. coloradoensis (see below), the specimen is identified as the former. Further review of variation in the p3 enamel patterns of B. idahoensis is needed.

Discussion— Brachylagus is distinguished from most extant and fossil North American leporids by the lack of an anterior reentrant on the p3 ( Kurtén and Anderson 1980, Ramos 1999a). The extinct genus Hypolagus is similar in some qualitative aspects to an extinct form of Brachylagus ( B. coloradoensis ) but is larger in size ( Ramos 1999b). Until recently, the genus Brachylagus was considered monotypic, with B. idahoensis as the only recognized species ( Ramos 1999b).

Fossils of Brachylagus idahoensis are known only from the western United States and most fall within or near the present distribution of the species ( Kurtén and Anderson 1980). Exceptions are the records from Isleta Cave No. 2 and Sheep Camp Shelter in New Mexico ( Harris 1993). The occurrence of B. idahoensis at Cathedral Cave was previously noted by Ramos (1999b).