Onthophagus curvicornis Latreille 1812

Onthophagus curvicornis species group*. This group is diagnosed by a male protibial apex with some short setae (Figs. 1.1-7); pronotum hornless; apical and internal margin of male protibia with a bulge ending in an acuminate projection (Figs. 1.1-7); male protibial spur downward bent at apex (Figs. 1.1-7); metafemur very short and stout (Figs. 2.1-7); apex of parameres poorly developed and defined. Rossini et al. (2018a) recognized the O. curvicornis species complex within the O. hircus species group based on morpho-anatomical traits observed on the external body and genital organs. This relationship is recovered in the present study, supporting its hierarchy as a species group and not at a species complex level. Our study of the protibiae shows that the O. curvicornis species group has a protibial acuminate apex (Fig. 1.1–7), whereas it is obsolete or with an obtuse tooth in the closely related O. hircus species group (Fig. 1.8 –15). In their Onthophagus study, Emlen et al. (2005: fig. 4) recovered the O. curvicornis species group based on O. acuminatus Harold, O. incensus Say, and O. stockwelli Howden & Young with a bootstrap support of 100 for the tree branch. Breeschoten et al. (2016) suggested a stem age of the group of around 14 Mya with a bootstrap value of 95. Schwery & O'Meara (2021) also recovered an O. curvicornis species group with a bootstrap support of 24. The present bootstrap analysis (Fig. 8) registers a clade node support of 35. At present, according to Rossini (2021) and Rossini et al. (2018a), eleven species are considered to belong to this new group (Table 7). In addition, six new species have been identified within this species group by Rossini et al. (2018a) and await description. This species group is distributed from the northern United States of America to northern Peru (through northern Venezuela), and two species from southeastern Brazil to northern Uruguay.