A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees Author Kohlmann, Bert 0000-0002-3441-3933 BioAlfa Barcoding Project Santo Domingo de Heredia, Costa Rica. bkohlmann64@gmail.com Author Solís, Ángel 0000-0002-3441-3933 BioAlfa Barcoding Project Santo Domingo de Heredia, Costa Rica. bkohlmann64@gmail.com text Zootaxa 2025 2025-03-17 5604 4 401 447 https://doi.org/10.11646/zootaxa.5604.4.1 journal article 309262 10.11646/zootaxa.5604.4.1 6cb6dc0a-77b3-4984-a365-6df139360b16 1175-5326 15213967 6A95109D-6F33-4DE7-9D47-6A722DD26918 Onthophagus hoepfneri species group* . This group is diagnosed by no male head horns present ( Fig. 5.14 ); male protibial apex with some sparse short setae subequal to apical spur ( Figs. 1.59 –66); pronotum with a small pointed or rounded anterior-pronotal projection ( Fig. 5.14 ); with coarse punctures in metafemur ( Figs. 2.59 –66). We propose, based on the barcode and morphological analyses, that this species group includes, at present, besides O. hoepfneri Harold , four more species, O. coscineus , Bates , O. oklahomensis Brown , O. pennsylvanicus Harold , and O. tuberculifrons Harold. Using a phylogenetic analysis, Emlen et al. (2005 : fig. 2, bootstrap support of 79) had already obtained a branch formed by O. coscineus and O. pennsylvanicus . At the same time, because of the low support values indicated by the maximum-likelihood tree ( Fig. 8 ), more species groups might emerge from the O. hoepfneri branch once more species are included. These maximum-likelihood analyses suggest the existence of at least two clades within this species group, one formed by O. coscineus and O. tuberculifrons , another by O. hoepfneri , O. oklahomensis , and O. pennsylvanicus . More specimens are needed to clarify this situation. Boucomont (1932) placed O. hoepfneri in his “8 e Groupe”, which corresponds to the O. landolti species group, and O. oklahomensis , O. pennsylvanicus , and O. tuberculifrons in his “12 e Groupe”; O. coscineus was unassigned. The relationship of the O. hoepfneri species group with the O. crinitus species group suggested in this study ( Figs. 1–2 ) was expected. In another maximum-likelihood genetic analysis, Emlen et al. (2005 : fig. 4, Bayesian posterior probability of 99) obtained a branch formed by O. crinitus and O. pennsylvanicus . The Emlen et al. (2005) analysis and the present barcode ( Figs 1–2 ) and partition ( Fig. 9 ) analyses suggest a close relationship between these two groups. Schwery & O'Meara (2021) also recovered a mixed O. hoepfneri – O. crinitus clade with a bootstrap support of 9. The O. hoepfneri species group is distributed from the United States of America to Ecuador .