Abstract
The Onthophagus mexicanus species group includes at least 18 species: O. anewtoni Howden and Génier, O. arnetti Howden and Cartwright, O. browni Howden, O. cartwrighti Howden, O. championi Bates, O. concinnus Castelnau, O. cynomysi Brown, O. eulophus Bates, O. guatemalensis Bates, O. hecate (Panzer), O. mcclevei Howden and Génier, O. medorensis Brown, O. mexicanus Bates, O. orpheus (Panzer), O. polyphemi Hubbard, O. pseudoguatemalensis sp. n., O. totonacus sp. n. and O. velutinus Howden and Cartwright. Onthophagus pseudoguatemalensis sp. n. and O. totonacus sp. n. are described from Mexico (Jalisco and Veracruz, respectively). Onthophagus cartwrighti, O. championi, O. eulophus and O. guatemalensis are redescribed, while lectotypes are designated herein for O. championi and O. eulophus. The distribution of O. cartwrighti is clarified; a new country record is provided for O. championi (Honduras); new state records are reported for O. championi (Oaxaca and Veracruz, Mexico) and O. guatemalensis (Oaxaca, Mexico). The accurate distribution of O. eulophus remains unknown since its original description. Updated distribution maps are included for all the species within the group. An updated determination key to species of the O. mexicanus species group is provided. The rarity of O. eulophus and O. totonacus in the entomological collections is thought to be a consequence of their trophic habits; both species are suggested to be inquilines of rodent nests or burrows.