taxonID	type	description	language	source
03AA23621471FF84FF28AC37FEEDABE2.taxon	diagnosis	This group is diagnosed by the male having no clypeal horn (Figs. 5.17 – 18); male clypeus transverse, with clypeal keel reduced or absent and long frontal keel; female clypeus less transverse with strong and forward-arched clypeal keel; male protibia apex having short setae (Figs. 1.45 – 55), male pronotum unarmed forming a large gibbosity (Figs. 5.17 – 18), and well-developed males presenting small head horns (Figs. 5.17 – 18). Zunino & Halffter (1988: 23) characterized this species group based on the male and female genitalia.	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA23621471FF81FF28ABCBFF71A9C4.taxon	diagnosis	This group is diagnosed by males having a clypeal horn (Fig. 5.3); frons of male and female with two horns; male protibia long and slender, with a tuft of long setae at the apex (Figs. 1.79 – 90); metatibial apex with short thick setae, alternating with thin setae of the same length as the thick setae, or longer, but never more than 2.5 times the size of the thick setae (Fig. 5.5); anteriosuperior region of male and female pronotum with two medial keels or humps; pronotum and elytral interstriae smooth with feeble punctures, with metallic luster (evanescent in O. andersoni Howden & Gill and O. grataehelenae Kohlmann & Solís); pygidium finely punctate.	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA2362147BFF8EFF28AEB8FE9CAC02.taxon	diagnosis	This group is diagnosed by the male having no clypeal horn and with two curved horns at the vertex (Fig. 5.6); male protibia apex with a tuft of long setae (Fig. 1.56); metafemur long and slender, bicolored, dark brown at apices and light brown at the center (Fig. 2.56); long dorsal pubescence.	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA2362147BFF8EFF28AEB8FE9CAC02.taxon	discussion	Based on external morphology and genitalia, Rossini et al. (2018 a) proposed that O. crinitus Harold is related to the O. gazellinus species group. The present mtDNA barcode study (Figs. 1 – 2) and the gene tree analyses (Figs. 8 – 9) weakly support this genital morphology-based proposal (clade node value of 9). Boucomont (1932), in his Onthophagus species groups study, established a “ 6 e Groupe ” composed of O. crinitus and O. lebasi Boucomont. According to him, this group is characterized by setose species with long pubescence and the male having long and slender protibiae. Subsequently, Zunino & Halffter (1997) considered O. lebasi a member of the O. landolti species group. The maximum-likelihood analyses (Figs. 8 – 9) suggest that O. lebasi represents an indepent clade with a weak relation to Eastern Hemispheric species. The O. crinitus species group is distributed from Mexico to Colombia.	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA2362147BFF8EFF28AC68FCB7AAFB.taxon	diagnosis	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.	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA2362147BFF8EFF28AC68FCB7AAFB.taxon	discussion	Rossini et al. (2018 a) 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. (2018 a), 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. (2018 a) 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.	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA2362147BFF8FFF28AAE0FF71AA43.taxon	diagnosis	This group is diagnosed by males having a clypeal horn (Fig. 5.2); male protibia long and slender, with a tuft of long setae at apex (Figs. 1.67 – 78); metatibial apex with short, thick setae, alternating with thin setae of the same length as the thick setae, or longer, but never more than 2.5 times the size of the thick setae (Fig. 5.5); pronotum and elytral interstriae rough with coarse punctures, without metallic luster; pygidium with large coarse punctures, giving the impression of looking like a honeycomb.	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA2362147BFF8FFF28AAE0FF71AA43.taxon	discussion	Of note are the results of the barcode analyses. According to the greatest interspecific and intergroup genetic distances in this study, these are concentrated between the O. dicranius and O. chevrolati species groups. This would support, according to previous evidence, that O. dicranius, together with O. clypeatus, its suggested sister group, are the oldest Western Hemispheric species groups, whereas O. chevrolati would represent the most recent species group in the Western Hemisphere. The O. dicranius species group is distributed from Mexico to Ecuador (Génier 2017).	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA2362147AFF8FFF28AAA8FA83A84B.taxon	diagnosis	This group is diagnosed by a slightly emarginate clypeus; apical and internal male protibial margins projected (Figs. 1.23 – 25); male protibial apex with some short setae (Figs. 1.23 – 25); male protibial spur strongly bent inwards (Figs. 1.23 – 25); male pronotum with a horn or a plate-like horn, which is level or turned upwards, never bent downwards.	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA2362147AFF8FFF28AAA8FA83A84B.taxon	discussion	Although no species of this group could be included in the mtDNA analysis, this aggregation is established based on a characteristic set of morphological characters, like having apical and internal male protibial margins projected and a male protibial spur strongly bent inwards (Figs. 1.23 – 25). Moreover, contrary to the O. mexicanus species group that have long and slender male protibiae (Figs. 1.26 – 28), this group has short and stout male protibiae (Figs. 1.23 – 25). All species of this group seem to be associated with rodent nests; this behavior is supported by the shortened male protibiae and bent male protibial spurs (Moctezuma & Halffter 2021; Moctezuma et al. 2023). We consider that this group includes eight species (Table 7). Zunino & Halffter (1997) and Moctezuma & Halffter (2021) consider these species part of the O. mexicanus species group. The O. eulophus species group is primarily distributed in the mountains of the southwestern United States of America and along the Mexican Pacific mountain slopes, except for O. totonacus Moctezuma & Halffter, which lives along the Mexican Gulf piedmont.	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA2362147AFF8CFF28A850FEEBAEEB.taxon	diagnosis	This group is diagnosed by the male having no head horns (Figs. 5.7 – 8); male protibial apex with a tuft of long setae resembling a fine-pointed paintbrush (Figs. 1.57 – 58); pronotum with four transversely aligned tubercles along a straight carina (Figs. 5.7 – 8), base unrimmed; metafemur light brown with fine punctures (Figs. 2.57 – 58); at the excavated posterior pronotal margin a line of 5 – 6 large, ocellate punctures with one short, stiff, upward pointing seta, punctures disappearing towards middle of the pronotal margin; apex of elytra and pygidium with long, erect setae.	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA2362147AFF8CFF28A850FEEBAEEB.taxon	discussion	Boucomont (1932) initially established this species group as his “ 10 e Groupe ” and was supported by Kohlmann & Solís (2001) under the name of O. gazellinus species group. This group contains, at present, only two species, O. gazellinus Bates and O. onthochromus Arrow (Table 7). Boucomont (1932) defined the group as having large species with long erect setae at the end of the elytra and on the pygidium; male head unarmed and female with two carinae; thorax base not rimmed; coloration light, elytral points brown. This species group is distributed from Nicaragua to Brazil.	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA23621479FF8CFF28AEF0FACCAD07.taxon	diagnosis	This group is diagnosed by the apical and internal male protibial margin projected (Figs. 1.39 – 44); male protibial spur bent downwards (Figs. 1.39, 1.41 – 44); male protibial apex with some short setae (Figs. 1.39 – 44); male pronotum with a bifurcate projection bent downwards or level (Figs. 5.12 – 13).	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA23621479FF8CFF28AD6CFC62A84B.taxon	diagnosis	This group is diagnosed by a male protibial apex with some short setae (Figs. 1.8 – 15); apical and internal margin of male protibia obtuse or with obsolete tooth (Figs. 1.8 – 15) (O. confusus has long male protibiae with internoapical tooth distinct and acuminated); male protibial spur downward bent at the apex (Figs. 1.8 – 15); pronotum without horns; metafemur very short and stout (Figs. 2.8 – 15); apex of parameres poorly developed and defined.	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA23621479FF8CFF28AD6CFC62A84B.taxon	discussion	Zunino & Halffter (1997) established an O. hirculus species group, later renamed O. hircus by Rossini et al. (2018 a). Although Zunino & Halffter (1997) do not mention it, this group is based on and corresponds to the “ 5 e Groupe ” of Boucomont (1932), to which they erroneously incorporated O. crinitus. In the Rossini et al. (2018 a, 2018 b) study of the O. hircus species group, the authors established five species complexes: O. curvicornis, O. hircus, O. ophion, O. osculatii, and O. rubrescens. The present analysis recovers an O. hircus species group formed by species of the O. hircus, O. osculatii, and O. rubrescens species complexes. The O. curvicornis species complex is elevated to a group level in this study, as suggested by the present mtDNA analyses. No members of the O. ophion species complex could be analyzed. The present analysis needs to contain a significant enough sample of analyzed species to validate all the proposed O. hircus species complexes. This group presents a distribution from Mexico to the peripheral Amazonian basin of South America, including the Lesser Antilles. Interestingly, Emlen et al. (2005: fig. 4) recovered an O. hircus – O. nasutus clade in their phylogenetic analysis, thus suggesting a relationship between the two species groups. The present barcoding analysis (Figs. 1 – 2) recovers the same relationship, whereas the bootstrap (Fig. 8) and the partition (Fig. 9) analyses suggest the O. nasutus species group as a sister group to the O. clypeatus – O. dicranius species groups. A more comprehensive analysis is needed. Breeschoten et al. (2016) register an O. hircus species group with a bootstrap value of 61 with an estimated crown age of approx. 10.5 Mya and a stem age of approximately 14 Mya. Schwery & O'Meara (2021) recovered also an O. hircus species group with a bootstrap support of 74. Moctezuma et al. (2024) proposed a stem value of around 17.5 Mya for the species group and a crown value of around 11 Mya.	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA23621479FF8DFF28A850FAA5AFCB.taxon	diagnosis	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).	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA23621478FF8DFF28AFD0FCA4AAD7.taxon	diagnosis	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).	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA23621478FF8DFF28AADCFC71A917.taxon	diagnosis	group is diagnosed by a pale antennal club; head frons with a strong carina; elytral intervals having a median row of tubercles each bearing a strong seta; distal edges of the elytra have contrasting pale markings (brown in O. fragosus); the pygidium has distinct setiferous umbilicate punctures; males with a brush of fused long hair at the distal end of the protibiae. Its two species live in Cuba.	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA23621478FF8DFF28AADCFC71A917.taxon	discussion	Although no species of this group could be included in the mtDNA analysis, this aggregation is established based on a characteristic set of morphological characters mentioned in the diagnosis. The group is composed at present by O. marginatus Laporte and O. fragosus Génier & Howden. The first species is widely distributed on the island; the second has been collected in litter on an isolated patch of moist forest (650 - 935 m a. s. l.) (Matthews 1966; Génier & Howden 2014). There is also a third species in the Greater Antilles living in Hispaniola, O. albicornis Palisot. Matthews (1966) is of the opinion that the species of the Greater Antilles are derived from a common ancestor. This might be so because O. albicornis shares with the two Cuban species the following characters: distal edges of the elytra have contrasting pale markings (brown in O. fragosus); the antennal clubs are white while alive, turning yellowish when dead; prominent brush of fused setae emerging from the distal end of the male foretibia. Génier and Howden (2014) indicated that the protibiae of O. fragosus lacked the apical setal brush. However, photographs provided by Andrew Smith of the male O. fragosus clearly shows the existence of this structure.	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA23621478FF8AFF28A91CFA92AC03.taxon	diagnosis	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).	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA23621478FF8AFF28A91CFA92AC03.taxon	discussion	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.	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA2362147FFF8AFF28AC68FD7BA93B.taxon	diagnosis	This group is diagnosed by a male having a clypeal horn (Fig. 5.1); female frons never with a horn (either unarmed or with simple straight carina); male protibia short and stout, with a broad brush of setae at the apex subequal in length to the apical spur (Figs. 1.16 – 22); metatibial apex, with short thick setae, alternating with other thin and long setae three times or more the length of the thick setae (Fig. 5.4); female anterosuperior region of pronotum simple, never carinate.	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA2362147FFF8AFF28AC68FD7BA93B.taxon	discussion	The species forming this group were initially considered part of the O. clypeatus species group by Boucomont (1932), Zunino & Halffter (1981, 1997), and Kohlmann & Solís (2001). Zunino & Halffter (1981), when first establishing the existence of the O. clypeatus species group, indicated that the species belonging to the O. nasutus species group might belong to another (unnamed) group. They considered the following species as part of this possible different group: O. carpophilus Pereira & Halftter, O. nasicornis Harold, O. nasutus Guérin-Méneville, O. sharpi Harold, O. tapirus Sharp, and O. rostratus Harold. Subsequently, Howden & Gill (1987) considered the existence of an O. nasicornis – O nasutus species complex within the O. clypeatus species group. Delgado & Deloya (1990) proposed an O. nasutus line, separate from an O. clypeatus and O. mirabilis species lines, all three lines forming part of an O. clypeatus species group. Although their taxonomic discussion is not clear, they proposed within this O. nasutus line, an O. nasutus species complex formed by: O. atriglabrus, O. nasicornis, O. nasutus, and O. villanuevai. Later, Zunino & Halffter (1997) maintained this O. nasutus species group as the O. nasicornis species complex, a part of the O. clypeatus species group. Subsequently, Delgado et al. (2006) excluded the O. nasicornis species complex from the O. clypeatus species group (sensu Zunino & Halffter 1997) based on the lack of tubercles and horns on the vertex of males without formally establishing a species group. Finally, Rossini & Génier (2024) established two subgroups, O. clypeatus and O. nasutus, as part of the O. clypeatus species group. Whereas Rossini & Génier (2024) give a complete list of the species belonging to their O. clypeatus subgroup, they did not specify any species for their O. nasutus subgroup. The mtDNA barcode and maximum-likelihood analyses recover this group. The barcode analysis (Figs. 1 – 2, 6) suggests a relationship with the O. hircus species group. Emlen et al. (2005: fig. 4) and Schwery & O'Meara (2021: fig. 1) also suggested this same relationship. In contrast, the bootstrap and partition analyses propose a relationship with the O. clypeatus – O. dicranius species groups with a low node support value of 9. Unlike most Western Hemispheric Onthophagus, this species group is not coprophagous but, instead, frugivorous, mycophagous, necrophilous, and saprophagous. The Emlen et al. (2005: fig. 4) phylogenetic tree showed that O. sharpi Harold (O. nasutus species group) falls within a branch composed of O. haematopus Harold and O. marginicollis Harold (both species members of the O. hircus species group) with bootstrap support of 88; therefore, supporting the results presented in Fig. 1 and Fig. 2, where O. hircus and O. nasutus appear as sister species groups. Emlen et al. (2005: fig. 6 a) considered that O. sharpi gained a clypeal horn in an independent evolutionary process from the O. clypeatus species group. This species group is distributed from Mexico to Ecuador.	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA2362147FFF8BFF28A920FB90AC97.taxon	diagnosis	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.	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
03AA2362147FFF8BFF28A920FB90AC97.taxon	discussion	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.	en	Kohlmann, Bert, Solís, Ángel (2025): A review of the species groups of the Western Hemisphere Onthophagus Latreille (Coleoptera: Scarabaeidae: Scarabaeinae) using COI barcoding and gene trees. Zootaxa 5604 (4): 401-447, DOI: 10.11646/zootaxa.5604.4.1, URL: https://doi.org/10.11646/zootaxa.5604.4.1
