Key to species and subspecies of Canthon (Goniocanthon) Pereira & Martínez, 1956

1. Pygidium strongly convex. Metasternal anterior lobe convex or flat (Fig. 1). Dorsal surface glabrous with blue, green, golden, or red metallic sheen (Figs 2–4). Ventral surface of metafemur not marginate anteriorly …………………2 Canthon (Goniocanthon) Pereira & Martínez, 1956

– Pygidium flat or slightly convex. Metasternal anterior lobe, if protuberant, angled or truncated, not convex. Dorsal surface pubescent or glabrous, with or without metallic sheen. Ventral surface of metafemur marginate or not anteriorly ……………………………………………………………… ……other subgenera and isolated species-groups of Canthon sensu Halffter & Martínez (1977)

2. Both pygidium and metasternal anterior lobe strongly convex. Profemur with a tooth on its anterior lower border. Pronotum and elytra with similar colour. South America ……………3

– Only pygidium convex (Fig. 4C). Metasternal anterior lobe flat (Fig. 4B). Profemur without tooth on its anterior border (Fig. 4B). Pronotum metallic green and elytra bright black (Fig. 4A). Guyanas, Suriname, Venezuela …………………………………… C. (G.) bicolor Castelnau, 1840

3. Meso- and metafemora ventral surface completely smooth (Fig. 1A). Metasternal anterior lobe strongly convex in males (Fig. 1B). Dorsal surface with blue or green metallic sheen (Fig. 2). Brazil (from Ceará to Santa Catarina, westward till southern Mato Grosso do Sul), Argentina and Paraguay, along the Paraná River ……………………………………… C. (G.) smaragdulus (Fabricius, 1781)

A Dorsal surface with blue metallic sheen (Fig. 2A). Brazilian coastal Atlantic Forest (from southern Rio de Janeiro to Santa Catarina, westward to southern Mato Grosso do Sul), Argentina and Paraguay along the Paraná River …………… C. (G.) smaragdulus smaragdulus (Fabricius, 1781)

A’ Dorsal surface with green metallic sheen (Fig. 2B). Brazilian coastal Atlantic Forest (from Ceará to São Paulo) ………………………………… C. (G.) smaragdulus subviridis Schmidt, 1922 stat. rev.

– Meso- and metafemora ventral surface rugose on posterior half (Fig. 1D). Metasternal anterior lobe only slightly convex in males (Fig. 1E). Dorsal surface with green, golden, or red metallic sheen (Fig. 1E). Amazon forest in Bolivia, Brazil, Colombia, Ecuador and Peru ……………… ………………………………………………………………… C. (G.) fulgidus Redtenbacher, 1868

B Dorsal surface with only red metallic sheen, without green or golden reflexes (Fig. 3C). Northeastern Bolivia. Brazil (Acre, northern Mato Grosso, southern and central Pará, Rondônia) ……………………………………………………………… C. (G.) fulgidus pereirai subsp. nov.

B’ Dorsal surface with golden metallic sheen (Fig. 3A). Brazil (northern Mato Grosso) ………… …………………………………………………………… C. fulgidus fulgidus Redtenbacher, 1868

B’’ Dorsal surface with green metallic sheen, devoid of any orange, with sometimes slight golden reflection (Fig. 3B). Central Colombia, eastern Ecuador and Peru, and Brazil (western Amazonas) ………………………………………………… C. (G.) fulgidus martinezi subsp. nov.