An illustrated catalogue of South American species of the genus Omorgus Erichson is presented. Based on this study we propose the following taxonomic changes: Omorgus (Omorgus) capillaceus Scholtz, 1990, syn. nov. and Omorgus (O.) lucidus Pittino, 2010, syn. nov. are proposed as junior subjective synonyms of Omorgus (O.) fuliginosus (Robinson, 1941) and Omorgus (O.) ciliatus (Blanchard, 1847), respectively. Lastly, we designated a male neotype for the ubiquitous New World species Trox suberosus Fabricius, 1775 to replace the missing type.