Australian species of Scydmaenus Latreille in subgenera Choleropsis Franz, Kingius Franz, Mascarensia Franz, Parallomicrus Franz, and Scottiscydmaenus Franz are revised, and Ascydmaenus subgen. n. is described. The type species of Choleropsis was found to be Heterognathus geniculatus King, misidentified as H. gracilis King; H. geniculatus is selected as the type species of Choleropsis, and H. gracilis is placed in Scydmaenus (incertae sedis). Scydmaenus princeps (King) (previously in Cholerus), S. beechmonti Franz (previously in Cholerus), and S. kurandae Franz (previously in Scydmaenus s. str.) are transferred to Scydmaenus (Choleropsis). Scydmaenus gracilis sensu Franz and S. princeps sensu Franz were found to be, in fact, misidentified specimens of S. geniculatus (King). The following species are redescribed or described as new: Scydmaenus (Choleropsis) geniculatus, S. (Choleropsis) princeps, S. (Choleropsis) beechmonti, S. (Choleropsis) kurandae, S. (Choleropsis) curviclavatus sp. n., S. (Choleropsis) kroombitanus sp. n., S. (Mascarensia) australiensis Franz, S. (Kingius) carinatus (King), S. (Kingius) formicarum Franz, S. (Parallomicrus) inflatitibia Franz, S. (Parallomicrus) myrmecobius Csiki, S. (Scottiscydmaenus) clarkianus Franz, S. (Scottiscydmaenus) optatus Sharp, S. (Scottiscydmaenus) swanensis Franz, S. (Scottiscydmaenus) brachyponerophilus sp. n., S. (Ascydmaenus) subglabratus sp. n., and S. (Ascydmaenus) haigensis sp. n. Two Australian species previously placed in Scydmaenus are transferred to Euconnus Thomson, resulting in Euconnus (Tetramelus) armitagei (King) comb. n., and Euconnus (incertae sedis) macleayii (King) comb. n. Two new synonyms were found: Scydmaenus marwillumbali Franz syn. n. is placed as a junior synonym of S. princeps (King), and Scydmaenus scottides Newton syn. n. (= S. scotti Franz) is placed as a junior synonym of S. optatus Sharp. Lectotypes are designated for Heterognathus gracilis King, H. geniculatus King, H. princeps King, Scydmaenus carinatus Sharp, Heterognathus myrmecophilus Lea, Scydmaenus optatus Sharp, and Scydmaenus swanensis Franz. Some misidentified specimens are excluded from the type series of Heterognathus princeps, Scydmaenus clarkianus, and S. swanensis.
