New Guinea Onthophagus: taxonomy of ten small, unicolored new species (Coleoptera: Scarabaeidae: Scarabaeinae).

The taxonomy of small, unicolor brown to black Papuasian species of the genus Onthophagus Latreille, 1802 is discussed. Two multi-species groups are defined in the nominotypical subgenus Onthophagus, one with broad and one with narrow dorsal eye foramina (O. acerus and O. kokodentatus groups, respectively). Twelve species are listed, keyed, and diagnosed. Ten of these are new species from Papua New Guinea (PNG) and West New Guinea (WNG, Indonesia), here described in the Onthophagus acerus group: O. aceroides (WNG), O. baiyericus (PNG), O. bituberoculus (WNG), O. daymanus (PNG), O. kokocellosus (PNG), O. kokopygus (PNG); in the Onthophagus kokodentatus group: O. dissidentatus (PNG), O. kokodentatus (PNG), O. kukali (PNG); and an ungrouped new species: Onthophagus ofianus (PNG). Two previously named species, O. acer Gillet, 1930 and O. mimikanus Balthasar, 1969, are briefly diagnosed and discussed.