Morphological variation was examined in 65 species of Canthon Hoffmansegg and 31 species in 11 additional genera of the tribe Canthonini (Anisocanthon Martínez & Pereira, Canthonella Chapin, Cryptocanthon Balthasar, Deltochilum Eschscholtz, Hansreia Halffter & Martínez, Holocanthon Martínez & Pereira, Malagoniella Martínez, Megathopa Eschscholtz, Melanocanthon Halffter, Scybalocanthon Martínez, and Sylvicanthon Halffter & Martínez). Morphological characters were examined on a total of 306 specimens. Variation in head structures such as clypeus, eyes, labium. gula, and epipharynx is described. Thoracic structures examined include pronotum, proepimeron, prosternum, and posterior and medial tibiae. Additional structures examined were the elytra, pygidium, and male genitalia, including the sclerites and brushes of the internal sac. Cladistic analysis of 39 taxa and 82 characters resulted in eight most parsimonious cladograms. The consensus tree confirms that Canthon is polyphyletic. Characters mainly from the epipharynx support the clade where most of the genera of Canthonini included in the analysis, with the exception of Cryptocanthon and Canthonella, are grouped. The species of the subgenus Francmonrosia form a clade supported mainly by synapomorphies from the internal male genitalia. Species of the genus Scybalocanthon share four synapomorphies with Canthon sordidus. Although there are some supported groups, there is extensive homoplasy in the cladogram mainly for characters of external morphology. A majority of the synapomorphies correspond to characters from the internal structures such the epipharynx and the internal male genitalia. Therefore we consider the internal morphology to be more informative in defining natural groups within Canthonini.