Onthophagus velutinus Horn 1875

Onthophagus velutinus species group*. This group is diagnosed by a pronotal disc distinctly tuberculate; clypeus slightly emarginate; surface of pronotum and (or) elytra finely alutaceous. Male with two straight and erect horns at vertex (Figs. 5.19 –20); male protibia short and stout (Figs. 1.29 –30); male protibial spur inwardly bent at apex (Figs. 1.29 –30); male protibial apex with some short setae (Figs. 1.29 –30); metafemur long and slender (Figs. 2.29 –30); male pronotum with a well-developed central gibbosity (Figs. 5.19 –20); apex of parameres well developed and defined. Females with carina of vertex nearly straight. Zunino & Halffter (1997: 159) included O. velutinus Horn as part of the O. mexicanus species group without giving any justification for this decision. Later, Zunino (2003) considered O. cartwrighti Howden to be in an incertae sedis species group. Subsequently, Moctezuma & Halffter (2019) suggested that O. cartwrighti should be included within the O. mexicanus species group due to its close relationship to O. velutinus. We disagree with these opinions because these species have a different Bauplan (from the German, Bauplan (s.) [Baupläne, pl.], body plan, a suite of characters shared by a group of phylogenetically related animals at some point during their development; Willmore 2012) from the O. mexicanus species group. While the mtDNA analyses suggested a relationship between the O. velutinus and O. mexicanus species groups (Figs. 1–2, 8–9), the external morphological Bauplan between these two groups is entirely different. The O. velutinus species group, contrary to the O. mexicanus species group, does not have pronotal horns and no short and thick metafemora (Figs. 2.29 –30) and presents very characteristic and almost parallel long vertex horns (Figs. 5.19 –20). Howden & Cartwright (1963: 107) indicated that O. velutinus is quite distinct from other Western Hemispheric Onthophagus species and seemed restricted to Neotoma Say & Ord (Rodentia: Cricetidae) nests. We suggest that O. cartwrighti and O. velutinus form a new species group, the O. velutinus species group, distributed in the Southwestern United States of America and the Baja California Peninsula.