A monographic revision of the Neotropical dung beetle genus Sylvicanthon Halffter & Martínez, 1977 (Coleoptera: Scarabaeidae: Scarabaeinae: Deltochilini), including a reappraisal of the taxonomic history of ‘Canthon sensu lato’

Abstract

Although extensively studied by different authors over the past 150 years, the taxonomy of Canthon Hoffmannsegg, 1817 and allied genera (which are here informally referred to as ‘Canthon sensu lato’) still remains problematic. With the aim of resolving some of the questions surrounding these taxa, the present work reviews the taxonomy of one of them, the genus Sylvicanthon Halffter & Martínez, 1977. As defined here, Sylvicanthon is distributed mainly throughout the vast areas of tropical rainforests in the Neotropical region and includes 15 species divided into two groups: the enkerlini group, with a single species, S. enkerlini (Martínez et al., 1964) comb. nov., and the candezei group, with five subgroups: the candezei subgroup, with S. candezei (Harold, 1869), S. genieri sp. nov. and S. foveiventris (Schmidt, 1920); the aequinoctialis subgroup, with S. aequinoctialis (Harold, 1868) comb. nov. and S. proseni (Martínez, 1949) stat. et comb. nov.; the bridarollii subgroup, with S. bridarollii (Martínez, 1949), S. seag sp. nov., S. edmondsi sp. nov. and S. attenboroughi sp. nov.; the furvus subgroup, with S. furvus (Schmidt, 1920), S. monnei sp. nov., S. mayri sp. nov. and S. obscurus (Schmidt, 1920); and the securus subgroup, with a single species, S. securus (Schmidt, 1920) comb. nov. Three species originally included in Sylvicanthon are here (re)transferred to Canthon: Canthon xanthopus Blanchard, 1846 and C. machadoi (Martínez & Pereira, 1967) comb. nov., as well as C. cobosi (Pereira & Martínez, 1960) stat. et comb. nov., which had been previously in synonymy under C. xanthopus. Descriptions, redescriptions, illustrations and comparative tables on the external morphology (including the genital capsule) of the genus and its species are presented, as well as a detailed discussion on their biogeography, comparative morphology, hypotheses on their phylogenetic relationships, data on natural history and a detailed historical revision of the classification of ‘Canthon sensu lato’. Finally, we also discuss the so-called ‘species problem’ (i.e., the definition of the scientific term ‘species’) and its consequences to dung beetle taxonomy and favour the solution offered by the Biological Species Concept.