Onthophagus landolti Harold 1880

Onthophagus landolti species group. This group is diagnosed by the male having no head horns (Fig. 5.14); male protibial apex with a tuft of long setae (Figs. 1.31 –38); pronotum with a small central protuberance (Fig. 5.14); metafemur brown to black with coarse punctures (Figs. 2.31 –38). This species group has been studied recently by Arriaga-Jiménez et al. (2020), within which they established the O. anthracinus species complex. According to Arriaga-Jiménez et al. (2020), the O. landolti species group comprises the following species complexes: O. anthracinus, O. lecontei – O. subopacus, and O. mariozuninoi, plus 18 unassigned taxa to species complexes. The O. landolti species group was established by Zunino & Halffter (1997) and is based on the Boucomont (1932) “8 e Groupe”. The species of this group have long, slender, and bent male protibiae with a tuft of long setae at their apex (Figs. 1.31 –38). In their Onthophagus analysis, Emlen et al. (2005: fig. 4) indicated that a branch formed by O. coscineus and O. knulli Howden & Cartwright (a member of the O. landolti species group) has a sister relationship with a branch formed by O. orpheus and O. hecate (no Bayesian posterior probability reported), thus supporting a relationship between the O. landolti and O. hecate species groups as suggested by this barcode study (Figs. 1–2). O. knulli has since been synonymized with O. durangoensis Balthasar by Arriaga-Jiménez et al. (2020). This last species is a member of the O. anthracinus species complex. On the other hand, Breeschoten et al. (2016) recovered in their study an O. landolti clade with a bootstrap support value of 99 and suggested a stem origin of the group of approximately 17 Mya. The present barcode (Figs. 1–2), bootstrap (Fig. 8), and partition (Fig. 9) analyses also suggest the existence of an O. landolti species group with a bootstrap value of 19. This low support node value suggests a similar situation as the one observed for the O. hoepfneri species group. It is highly possible that more species groups shall emerge from the O. landolti species group, once more species are added to the analysis. This group is distributed from the United States of America to Peru (Zunino & Halffter 1997).