In this article, the subgenus Canthon (Goniocanthon) Pereira & Martínez, 1956 is diagnosed within the tribe Deltochilini Lacordaire, 1856 and redefined with three species: 1) C. (Goniocanthon) bicolor Castelnau, 1840, from the Guyanas and northern South America, included for the first time in this subgenus; 2) C. (G.) smaragdulus (Fabricius, 1781), including two subspecies, C. (G.) smaragdulus smaragdulus, senior synonym of Canthon speculifer Castelnau, 1840 (neotype here designated), from the southern portion of the Atlantic Forest and C. (G.) smaragdulus subviridis Schmidt stat. rev. (lectotype here designated) from the northern portion of the Atlantic Forest; 3) C. (G.) fulgidus Redtenbacher, 1868, which includes three subspecies, C. (G.) fulgidus fulgidus from the southern Amazon (lectotype here designated), C. (G.) fulgidus martinezi subsp. nov., from the central and southern Amazon and C. (G.) fulgidus pereirai subsp. nov., from the western Amazon.

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A new species of Canthon is described, illustrated and the morphological similarities with related species are discussed. The species Canthon cleidecostae was named after Dr. Cleide Costa a great beetles specialist. The subgeneric category of species is considered incertae sedis until the taxonomic revision of the genus Canthon is fully addressed. Also, we provide a key for genera, subgenera and isolated species-groups that can be confused with the genus Canthon.

Canthon (Peltecanthon) is revised in this work. The subgenus now includes four species: C. (P.) staigi (Pereira, 1953), C. (P.) haroldi nom. nov., C. (P.) splendidus Schmidt, 1922 and C. (P.) terciae sp. nov. All species occur in the Atlantic Forest. Maps, natural history information, specimen data and illustrations are provided.

The genus Tetraechma Blanchard, 1842 is revised for the first time, and species distribution data updated. Three species previously placed in Canthon are transferred to Tetraechma; T. balteata (Boheman, 1858), comb.n., T. chlorophana (Mannerheim, 1829), comb.n., T. liturata (Germar, 1822), comb.n.. Canthon balteatus lojanus Balthasar, 1939 is considered a syn.n. of T. balteata, Canthon apicalis Lucas, 1859 is considered a syn.n. of T. chlorophana, and Ateuchus pictus Mannerheim, 1929 as syn.n. of T. liturata. Lectotypes are designated for Tetraechma sanguineomaculata Blanchard, 1845; Canthon balteatus Boheman, 1858, C. balteatus lojanus Balthasar, 1939, Canthon apicalis Lucas, 1859, Ateuchus chlorophanus Mannerheim, 1829, Ateuchus lituratus Germar, 1822, Canthon lituratus solutus Schmidt, 1920, Canthon lituratus solutus Schmidt, 1920, Canthon lituratus bifasciatus Schmidt, 1920 and Ateuchus pictus Mannerheim, 1929. Tetraechma, which was known only from two endemic species from Argentina, now has five species distributed from northern Colombia and Venezuela to the northern coast of Argentina.