Key to South American Trogidae genera:

1 Antennae with round scape (Figure 1c); margin of head evenly rounded, not angled at clypeogenal junction; lateral and posterior margins of pronotum with distinctive spatulate setae ............................................................................................................ genus Trox Fabricius

1’ Antennae with elongate scape (Figure 1a,b); margin of head usually angled at junction of clypeus and gena; lateral and posterior margins of pronotum with small filiform setae .......................................................................................................................................... 2

2 Antennae with pedicel attached subapically in the scape (Figure 1b); scutellum constricted at base (Figure 1e) or oval (Figure 1f); sixth antennomere without any seta ventrally; apex of clypeus reflexed or straight ........................ genus Omorgus Erichson

2’ Antennae with pedicel attached apically in the scape (Figure 1a); elongate scutellum (Figure 1d) or reduced (for species without humeral callus); sixth antennomere with a single seta ventrally (Figure 1a); apex of clypeus bent downwards, forming a right angle with the front ................................................................ genus Polynoncus Burmeister 3