Onthophagus mexicanus Bates 1887

Onthophagus mexicanus species group. The males of this group have a slightly emarginate clypeus (O. mexicanus), or a small clypeal projection (O. championi), or a distinct vertical clypeal horn protrusion present in O. guatemalensis and O. pseudoguatemalensis (Fig. 5.11); slender male protibiae (Figs. 1.26 –28); apical and internal male protibial margin acuminate (Figs. 1.26 –28); male protibial apex with some short setae (Figs. 1.26 –28); male pronotum with a plate-like projection, distally more-or-less distinctly emarginated at middle (Fig. 5.11). Zunino & Halffter (1988) established this species group based on the Boucomont (1932) “7 e Groupe”. Zunino & Halffter (1997) later defined this group, giving a detailed morphological characterization. Interestingly and opposed to this study, they considered that contrary to groups such as O. clypeatus and O. landolti, this group had a robust internal homogeneity that did not allow for the separation of species groups. Bates (1887) described in the Biologia Centrali-Americana for the first time an O. mexicanus species group comprised of O. championi Bates, O. eulophus Bates, O. guatemalensis Bates, and O. mexicanus Bate s. Moctezuma & Halffter (2021) considered that the group included at least 18 species. We consider the existence of only four species in this group (Appendix 1). The present analysis proposes the idea that at least three new species groups previously considered to form part of the O. mexicanus species group exist within: O. eulophus, O. hecate, and O. velutinus (Figs. 1–2). The present barcode and gene tree analyses (Figs. 1–2, 8–9) suggest a very close relationship between the O. mexicanus and O. velutinus species groups with a bootstrap support of 93, while the O. hecate species group is distantly related. The O. mexicanus species group is distributed in the mountains from northwestern Mexico to Costa Rica.