The monophyly of the Neotropical entimine weevil genus Exophthalmus Schoenherr, 1823 (Curculionidae: Entiminae: Eustylini Lacordaire) is reassessed. Exophthalmus presently includes more than 80 species, approximately half of which are restricted to either the Caribbean archipelago or the continental Neotropics. The taxonomic composition and position of Exophthalmus have been subject to longstanding disagreements; in particular, authors have questioned the relationship of Exophthalmus to other Caribbean genera such as Diaprepes Schoenherr, 1834 (Eustylini) and Lachnopus Schoenherr, 1840 (Geonemini Gistel), as well as to the speciose Central and South American genera Compsus Schoenherr, 1823, Eustylus Schoenherr, 1842, and Exorides Pascoe, 1881 (all Eustylini), among others. The present study scrutinizes these traditional perspectives, based on a cladistic analysis of 143 adult morphological characters and 90 species, representing 30 genera and seven tribes of Neotropical entimine weevils. The character matrix yielded eight most-parsimonious cladograms (length = 239 steps; consistency index = 66; retention index = 91), with mixed clade support that remains particularly wanting for some of the deeper in-group divergences. The strict consensus supports the existence of a paraphyletic Geonemini ‘grade’ that includes Lachnopus and related Caribbean genera such as Apotomoderes Dejean, 1834, followed by a monophyletic Eustylini in-group clade. Within the latter, a monophyletic South American Eustylini clade – including Compsus, Eustylus, Exorides, and related genera – is sister to a major clade that contains a ‘grade’ of heterogeneous and often misclassified Caribbean members of the Eustylini, Geonemini (Tetrabothynus Labram & Imhoff, 1852 and Tropirhinus Schoenherr, 1823), and Tanymecini Lacordaire (Pachnaeus Schoenherr, 1826), as well as two major clades: one with the majority of Central American Exophthalmus species, and the other with most Caribbean members of Exophthalmus. The Central American Exophthalmus clade is paraphyletic with respect to Chauliopleurus Champion, 1911 (Geonemini) and Rhinospathe Chevrolat, 1878 (Phyllobiini Schoenherr). The Caribbean clade, in turn, contains two subclades: i.e. (1) the Greater Antillean Exophthalmus s.s. clade, including the type species Exophthalmus quadrivittatus (Olivier, 1807); and (2) the primarily Lesser Antillean Diaprepes. The latter genus is therefore nested within Central American and Caribbean species of a highly paraphyletic Exophthalmus, yet may be rendered monophyletic if several Lesser Antillean Exophthalmus species are (re-)assigned to Diaprepes. The results thus provide a suitable basis for a revision of all Exophthalmus species, and furthermore suggest that historical biographic factors, including colonization via temporary continental Neotropics-to-Caribbean land connections, were important in the evolution of major eustyline lineages. Based on these preliminary insights, the following taxonomic and nomenclatural adjustments are made. Compsoricus gen. nov. is erected to accommodate two Puerto Rican species erroneously assigned to Compsus: i.e. the herein designated type species Compsoricus maricao comb. nov. and Compsoricus luquillo comb. nov. Eustylus dentipes comb. nov. is transferred from Compsus. Diaprepes marginicollis Chevrolat, 1880 is reinstated from synonymy under Exophthalmus. Lastly, the following five transfers are proposed: (1) Chauliopleurus Champion, 1911, from Geonemini to Eustylini; (2) Tetrabothynus Labram & Imhoff, 1852, from Geonemini to Eustylini; (3) Tropirhinus Schoenherr, 1823, from Geonemini to Eustylini; (4) Rhinospathe Chevrolat, 1878, from Phyllobiini to Eustylini; and (5) Pachnaeus Schoenherr, 1826, from Tanymecini to Eustylini.
© 2012 The Linnean Society of London, Zoological Journal of the Linnean Society, 2012, 164, 510–557.