Tachyoryctes Rüppell, 1835 . Neue wirbelth. Fauna Abyssin. Gehörig., Säugeth., 1:35, footnote.

TYPE SPECIES: Bathyergus splendens Rüppell, 1835 .

SYNONYMS: Chrysomys .

COMMENTS: Hollister (1919:40) listed eight species of Tachyoryctes, noting that "all have constant characters of differentiation, and intergradation between any two of them is not indicated by this material," and speculated that the "numerous forms will doubtlessly be connected by complete chains of intergrades and the final monographer of the genus will be obliged to reduce many of the named forms to the rank of subspecies." Allen (1939) and Ellerman (1941) listed 14 species of Tachyoryctes, but these were reduced to T. macrocephalus and T. splendens by Misonne (1974) who was followed by Corbet and Hill (1991). Of the twenty forms described, Rahm (1980) considered about 16 of them to be valid subspecies of T. splendens.

This change from 14 to 2 species was not based on careful analyses of morphological variation characterizing the named forms. Aside from Bekele's (1986) inconclusive univariate analyses of craniometric data from samples of Tachyoryctes, no assessment of morphological variation in the genus is available in context of a systematic revision. Until such a study provides documentation and definition of specific limits and their geographic distributions, we return to a modifed treatment of the arrangement by Allen (1939) and Ellerman (1941), which reflects the diagnostic information now available.