1. Elytra entirely dark brown. Venezuela (Amazonas)................. G. brunneus Joly, 2017

1 ʹ. Elytra yellowish brown with or without darker brown areas........................................ 2

2. Prothorax with lateral tubercles more projected and slightly acute at apex in males, slightly elevated and rounded at apex in females (Figs. 1–2). Mexico, Honduras, Costa Rica, Panama, Colombia (Cundinamarca, Valle del Cauca), Suriname, Guyana, French Guiana, Ecuador, Peru........ G. conicicollis Tippmann, 1953

2 ʹ. Prothorax without lateral tubercles........... 3

3. Distance between superior ocular lobes greater than width of upper ocular lobe; sides of prothorax converging anteriorly; pronotum covered by dense pubescence (except on surface of tubercles); humeri and elytral apices concolorous with remaining elytral surface (Figs. 3–7). Mexico (Veracruz)................................ G. cummingi Botero, Le Tirant, and Santos-Silva, new species

3 ʹ. Distance between superior ocular lobes smaller than width of upper ocular lobe; sides of prothorax subparallel; pronotum with glabrous or nearly glabrous central area; humeri and elytral apices dark brown (Fig. 8). Nicaragua, Costa Rica, Panama, Colombia (Vichada), Venezuela, Suriname, Guyana, French Guiana, Ecuador, Peru, Bolivia, Brazil (Amazonas, Pará, Maranh~ ao).................................... G. flabellicornis (Zajciw, 1965)