Taxonomic revision of <i>Dichotomius (Cephagonus)</i> Luederwaldt 1929 and the taxonomic status of remaining <i>Dichotomius</i> Hope 1838 subgenera (Coleoptera: Scarabaeidae: Scarabaeinae: Dichotomiini)

<i>Dichotomius</i> nomenclature is revised under the light of comparisons between type material and large series vouchered in several museums. Its division into four subgenera is redefined as follows: <i>Dichotomius</i> s. str., <i>Selenocopris</i> Burmeister, <b>revised status</b>, <i>Cephagonus</i> Luederwaldt <b>revised status</b> and <i>Homocanthonides</i> Luederwaldt. The species formerly in the subgenus <i>Selenocopris</i> (sensu Martínez 1951), except for those belonging to the <i>D. bicuspis</i> species-group, are transferred to <i>Cephagonus</i>, of which <i>Pinotus fissus</i> Harold is designated as type-species. <i>Cephagonus</i> has now 40 species: 38 spp. in five species groups: <b>1)</b> <i>D. ascanius</i> species-group (includes <i>D. ascanius</i> (Harold), <i>D. mundus</i> (Harold) and <i>D. socius</i> (Luederwaldt)); <b>2)</b> <i>D. fissus</i> species-group (includes <i>D. fissus</i> (Harold), <i>D. fonsecae</i> (Luederwaldt), <i>D. baiano</i> <b>n. sp</b>., <i>D. fernadosilvai</i> <b>n. sp</b>., <i>D. filgueirasi</i> <b>n. sp</b>. and <i>D. seag</i> <b>n. sp.; 3)</b> <i>D. quadraticeps</i> species-group (includes <i>D. quadraticeps</i> (Felsche), <i>D. semicircularis</i> (Luederwaldt) <i>D. aielloae</i> Nunes, <i>D. clypeatus</i> (Luederwaldt) and the cryptic species <i>D. fissiceps</i> (Felsche), <i>D. reichei</i> (Harold), <i>arnaudi</i> <b>n. sp</b>., <i>D. asenjoi</i> <b>n. sp</b>., <i>D. barbarae</i> <b>n. sp</b>., <i>D. blancoi</i> <b>n. sp</b>., <i>D. candango</i> <b>n. sp</b>., <i>D. edmondsi</i> <b>n. sp</b>., <i>D. frizzasae</i> <b>n. sp</b>., <i>D. gardneri</i> <b>n. sp</b>., <i>D. feeri</i> <b>n.sp</b>., <i>D. furtadoi</i> <b>n. sp</b>., <i>D. emas</i> <b>n. sp</b>., <i>D. marcoscarvalhoi</i> <b>n. sp</b>., <i>D. paschoali</i> <b>n. sp</b>., <i>D. ricardosilvai</i> <b>n. sp</b>., <i>D. tissianiae</i> <b>n. sp.; 4)</b> <i>D. ingens</i> species-group (includes the brachypterous species <i>D. ingens</i> (Luederwaldt), <i>D. darwini</i> Nunes &amp; Vaz-de-Mello, <i>D. manni</i> Nunes &amp; Vaz-de-Mello, <i>D. paresi</i> Nunes &amp; Vaz-de-Mello and <i>D. periotoi</i> Nunes &amp; Vaz-de-Mello) and <b>5)</b> <i>D. spadiceus</i> species-group (includes <i>D. spadiceus</i> (Luederwaldt), <i>D. itatiaiaensis</i> <b>n. sp</b>. and <i>D. lucianomourai</i> <b>n. sp</b>.). Two new species, <i>D. rondoniaensis</i> <b>n. sp</b>. and <i>D. vargasae</i> <b>n. sp</b>. are described but not assigned to any species-groups. Lectotypes are designated for <i>Pinotus ascanius piceus</i> Luederwaldt (<b>n. syn</b>. of <i>D. bicuspis</i>), <i>Pinotus ascanius</i> Harold, <i>Pinotus ascanius pygidialis</i> Luederwaldt (<b>n. syn</b>. of <i>D. ascanius</i>), <i>Pinotus mundus</i> Harold, <i>Pinotus simulans</i> Luederwaldt (<b>n. syn</b>. of <i>D. mundus</i>), <i>Pinotus socius</i> Luederwaldt, <i>Pinotus fissus</i> Harold, <i>Pinotus transiens</i> Luederwaldt (<b>n. syn</b>. of <i>D. reichei</i> Harold), <i>Pinotus fissiceps</i> Felsche, <i>Pinotus acutircornus</i> Luederwaldt (<b>n. syn</b>. of <i>D. spadiceus</i>). Diagnoses, new species descriptions, identification key, illustrations and geographical data are provided for all <i>Cephagonus</i> species.