Three new species of Onthophagus Latreille, 1802 from Bioko Island, Equatorial Guinea, belonging to d’Orbigny’s group IX, with a taxonomic note on O. denudatus d’Orbigny, 1902 (Coleoptera: Scarabaeidae: Scarabaeinae: Onthophagini)

Three new dung beetle species (Onthophagus basilensis Génier sp. nov., O. castus Génier sp. nov., O. larseni Génier sp. nov.) are described from Bioko Island, Equatorial Guinea, and assigned to d’Orbigny’s group IX. Specimens were collected in montane and lowland rainforest using dung-baited pitfall traps. Diagnostic characters, including male genitalia and intraspecific variation, are provided. A review of related taxa indicates that O. denudatus d’Orbigny, 1902 and O. denudatus endroedii Frey,