Contributions to the taxonomy of Dichotomius Hope, 1838 (Scarabaeidae: Scarabaeinae: Dichotomiini): Description of a new subgenus and redefinition of Dichotomius sensu stricto species groups

ABSTRACT

Dichotomius Hope, 1838 is one of the most diverse and abundant genera of dung beetles (Scarabaeidae: Scarabaeinae) in the New World. It congregates about 200 species distributed from the northeastern United States to central Argentina, and is arranged into four subgenera: Dichotomius s. str., Cephagonus Luederwaldt, 1929, Homocanthonides Luederwaldt, 1929 and Selenocopris Burmeister, 1846. The subgenus nominotypical has seen the least progress in its taxonomy, with only 15% of species with information in a recent revision. Therefore, in this paper, using a protocol for taxonomic revision and reviewing the type material and more than 12,000 specimens from 32 entomological collections, we have divided Dichotomius s. str. into two subgenera. We describe Dichotomius (Luederwaldtius) new subgenus to encompass, the smallest species (less than 20 mm), 13 species which previously belonged to D. sensu stricto, four species of Dichotomius (Selenocopris), and several undescribed species. Dichotomius triangulariceps (Blanchard, 1846) is transferred to the subgenus Selenocopris based on characters of the male genitalia. The subgenus Dichotomius s. str., in its new, more restricted sense, is delimited to include approximately 73 species arranged into, 12 species groups, plus two incertae sedis species. For each group, its definition is presented with species composition and geographic distribution. The incertae sedis species, D. agesilaus (Waterhouse, 1891) and D. compressicollis (Luederwaldt, 1929) (lectotype designated) are revised; the following information is presented for them: taxonomic history, species’ citation in published literature, redescription of males and females, list of material examined, photographs of the external morphology, male genitalia, and distribution map.

Keywords:
Dung beetles; Male genitalia; Morphology; Neotropical; Systematics

Introduction

Dichotomius Hope, 1838 is a highly diverse and abundant genus of dung beetles (Coleoptera: Scarabaeidae: Scarabaeinae) in New World ecosystems. Exclusive to the Western Hemisphere, this genus has species in the northeastern United States to central Argentina, with the highest diversity in South America (Vaz-de-Mello, 1999; Génier, 2000; Vaz-de-Mello et al., 2011; Nunes and Vaz-de-Mello, 2019). Ecologically, Dichotomius species are part of the group of large tunnellers. They build their nests using a variety of substrates such as mammal feces, carcasses, fungi, and fruits. This group includes both diurnal and nocturnal species (Gill, 1991; Hanski and Cambefort, 1991; Nichols et al., 2008). These species are abundant in tropical forests, where they represent the dominant group in terms of biomass and number of dung beetle species in certain ecosystems (Gill, 1991; Génier, 2000). Currently, the genus consists of approximately 200 species, classified into four subgenera: Dichotomius sensu stricto, Dichotomius (Cephagonus) Luederwaldt, 1929, Dichotomius (Homocanthonides) Luederwaldt, 1929, and Dichotomius (Selenocopris) Burmeister, 1846 (Nunes and Vaz-de-Mello, 2019; Cupello et al., 2023).

The genus Dichotomius was proposed by Hope (1838) for species that had previously been placed in Copris Geoffroy, 1762. These species were said to be related to Scarabeus boreus Olivier, 1789, which is the type species of this genus by original designation. The proposal was based on the following characteristics: “head with two horns, clypeus bidentate or strongly incised; thorax blunted anteriorly, (pointed at the extended anterior angles), with three horns, the central obtuse and subemarginate, lateral horns obtuse; elytra with seven striae; body with ventral setae; coxae convex; tibiae widened apically”. The clypeal margin with two medial teeth was considered the main diagnostic characteristic of this genus, indeed the one which gave it its name. In the same publication, Hope suggested incorporating Copris species possessing a clypeal margin that is evenly curved and lacks medial clypeal teeth into the subgenus Holocephalus Hope, 1838, with Scarabeus eridanus Olivier, 1789 designated as the type species. Since the original description of Dichotomius, numerous species have been identified, but errors such as considering conspecific males and females as different species (due to the striking sexual dimorphism of the genus) have been pervasive, so bringing considerables chaos to the taxonomy of the genus.

Burmeister (1846) proposed three subgeneric names for Copris: Homocopris with Copris torulosus Eschscholtz, 1822 as the type species by original monotypy, and the subgeneric names Selenocopris and Chalcocopris, but did not fix the types for the latter. Additionally, Haldeman (1846) proposed the generic name Brachycopris based on a labral character, designating Scarabaeus carolinus Linnaeus, 1767 as the type species.

Erichson (1847) proposed the genus Pinotus for the species with seven elytral striae and lacking distinct teeth or transverse carinae on the posterior side of the metatibiae. The author did not designate the type species for this new genus. Erichson included in this new genus species from Dichotomius, as well as the subgenera Holocephalus, Chalcocopris, and Selenocopris. Erichson's classification was widely adopted and utilized during subsequent decades.

Lacordaire (1855) designated mentioned Copris carolinus (Linnaeus, 1767) as the type species of the genus Pinotus, but this is not the case, as the species was not among those explicitly cited for Pinotus by Erichson (1847). The identify of the type species is still an open issue; the earliest known potential fixation appeared in Martínez (1951), who cited Pinotus talaus Erichon, 1847, one of the two originally included species, as the type, but whether a prior fixation exists is to be determined (Lozano de la Rosa et al., 2024). Recently, Bouchard et al. (2024) fixed P. talaus Erichson, 1847 as the type species of Pinotus.

The first revision of Pinotus was conducted by Harold (1869). In this study, the author considers Dichotomius, Holocephalus, and Homocopris as synonyms of Pinotus. Von Harold (1869) also proposes elevating the subgenera Chalcocopris to a genus and generates the first list of Pinotus species included 50 species. Gillet (1909, 1911) suggests revalidating and elevating the subgenera Holocephalus to a genus.

Hermann Luederwaldt was a prominent taxonomist who published extensively on the genus Pinotus during the early 20th century (Luederwaldt, 1922, 1923, 1925, 1926, 1928, 1929, 1930, 1931a, 1931b, 1935). In 1929, the author conducted his taxonomic overview of the genus, recognizing 113 species and predicting that the number of species in the genus would surpass 130. The author’s significant contribution to the genus’s taxonomy involved its division into “sections” (from the Portuguese “seções”, currently considered as species groups) to facilitate further study. Furthermore, the author establishes two new subgenera for Pinotus, Homocanthonides, comprising a single species, Copris smaragdinus Perty, 1830, and Cephagonus, encompassing species bearing a bidentate clypeus, with angular margins instead of rounded lateral head margins. Additionally, the author recognizes two other subgenera, Pinotus sensu stricto and Selenocopris. After Luederwaldt’s work, significant contributions were made by Pereira (1942a, 1942b) who revised the “semiaeneus” and “bitiensis” species groups.

Martínez’s (1951) review of the generic and subgeneric nomenclatural history of the names led to several conclusions. Firstly, based on the Principle of Priority (Article 23 of the current Code; ICZN 1999), the valid generic name is Dichotomius Hope, 1838, instead of Pinotus Erichson, 1847, which, as we have seen, was by then in prevailing usage. Additionally, Homocopris and Brachycopris are also synonymous with Dichotomius. Martínez also validated Selenocopris as a subgeneric name and designated Copris bicuspis Germar, 1823 as its type species. Additionally, Cephagonus Luederwaldt, 1929 is proposed as a synonym for Selenocopris. According to Martínez, part of Selenocopris species studied by Luederwaldt (1929) lack a subgeneric name. Therefore, Martínez suggests the name Luederwaldtinia for these species. Finally, he agreed with the recognition of the subgenus Homocanthonides, originally proposed by Luederwaldt (1929). Altogether, Martínez agreed with Luederwaldt that Dichotomius consists of four subgenera, the only difference between the two authors lying in the nomenclature.

Pereira and Martínez (1960) proposed the genus Isocopris to include three species of Dichotomius with eight antennomeres. Recently, Rossini and Vaz-de-Mello (2017) added other species to this genus. Vaz-de-Mello et al. (2010) revalited Homocopris, recognizing it as a genus for another species previously placed in Dichotomius.

In the last five decades, species have been continuously described and many have been synonymized in Dichotomius. As a result, the taxonomy of the genus has become disorganized, making it one of the genera in Scarabaeinae most in need of a modern taxonomic revision (Martínez, 1951; Génier, 2000; Vaz-de-Mello et al., 2011; Cupello et al., 2023). In recent years, several authors have studied the genus following the “sections” scheme established by Luederwaldt (1929). Their work has contributed to the taxonomic revision of Dichotomius, clarifying the subgeneric classification and some species groups, or transferring some species to other genera (Vaz-de-Mello et al., 2010; Arias-Buriticá and Vaz-de-Mello, 2012, 2013, 2019, 2023; Maldaner et al., 2015; Rossini and Vaz-de-Mello, 2015, 2017, 2020; Nunes, 2016; Nunes et al., 2016; Vaz-de-Mello and Nunes, 2016; Valois et al., 2017, 2022, 2023; Maldaner et al., 2018; Nunes and Vaz-de-Mello, 2019; Montoya-Molina and Vaz-de-Mello, 2021).

Dichotomius is part of the tribe Dichotomiini, as defined by Tarasov and Dimitrov (2016). The tribe is diagnosed by the following combination of characters: (1) maxilla with stipital sclerite II with medial groove on its trace; surface of groove usually shagreened, (2) dorsal articular sclerite forming a longitudinal carina on the dorsal surface of the galea, (3) epipharynx with deep triangular notch anteriorly, (4) Elytron with eight distinctly visible striae; last striae bifurcates apically, total number of striae nine, (5) radial axis (RP) of hind wing strongly sclerotized on posterior portion; posterior sclerite of RP1 separated from RP1i, and (6) fronto-lateral-peripheral endophallite (FLP) elongated in frontal-rear plane, usually small, “C”-shaped, (7) ME large, ring-shaped in the horizontal plane.

Dichotomius can be distinguished from other genera with overall similar morphology including Canthidium Erichson, 1847, Copris Geoffroy, 1762, Homocopris Burmeister, 1846 and Ontherus Erichson, 1847 based on its typically conical and bifurcated ventral clypeal process. For the closely related genera of the tribe Dichotomiini, Dichotomius can be separated from Chalcocopris Burmeister, 1846 and Isocopris Pereira & Martínez, 1960 by the antennae with nine antennomeres, and from Holocephalus Hope, 1838 by the second labial palpomere being triangular, not expanded (Luederwaldt, 1929; Vaz-de-Mello et al., 2010, 2011; Rossini and Vaz-de-Mello, 2015, 2017; Nunes and Vaz-de-Mello, 2019).

Nunes and Vaz-de-Mello (2019) conducted the most recent revision at a subgeneric level of Dichotomius, redefining them. As a result, the genus is divided into four subgenera proposed by Luederwaldt (1929): Dichotomius s. str., comprising 67 species in 11 species groups plus three incertae sedis species, (five recently revised: Arias-Buriticá and Vaz-de-Mello 2019, 2023, 2024a, 2024b; Rossini and Vaz-de-Mello, 2020); Dichotomius (Selenocopris), including 78 species in 15 species groups (eight revised: Nunes and Vaz-de-Mello, 2013; Maldaner et al., 2015; Nunes et al., 2016; Valois et al., 2017, 2022, 2023; Cassenote et al., 2020; Montoya-Molina and Vaz-de-Mello, 2021); Dichotomius (Cephagonus), with 41 species in five species groups (all revised: Nunes and Vaz-de-Mello 2019); and the monobasic Dichotomius (Homocanthonides) (revised: Maldaner et al., 2018).

The taxonomic revision of the subgenus Dichotomius s. str. lags the others. Of its 11 species groups, only five have been the subject of recent taxonomic revisions, 21 species studied, representing 27.6% of the known species in the subgenus (Arias-Buriticá and Vaz-de-Mello, 2019, 2023, 2024a, 2024b; Rossini and Vaz-de-Mello, 2020). Furthermore, species group definitions and characteristics need clarification, and the subgenus requires immediate taxonomic revision (Génier, 2000; Arias-Buriticá and Vaz-de-Mello, 2012, 2013, 2019, 2024a, 2024b; Nunes and Vaz-de-Mello, 2019; Rossini and Vaz-de-Mello, 2020).

This paper presents the first step towards a complete revision of the subgenus Dichotomius s. str., a redefinition of its taxonomy at the species-group level. The study is based on the external morphology of males and females and the morphology of the male sexual organs, and includes new division of species groups. The definition, species composition, and geographic distribution for each species group are provided to facilitate a future revision of Dichotomius s. str.

Materials and methods

Our ongoing investigation of the systematics of Dichotomius has been conducted based on the examination of nearly 12,000 specimens deposited in the following entomological collections (names of the curators and collaborators of each collection who assisted the authors on the dates of their visits are in parentheses, ^† = deceased researcher). Collections with an asterisk next to their abbreviation are those whose specimens were examined for this particular article. As for the other collections, the material has been examined but no specimens are cited in this article, and the material will be mentioned in subsequent articles:

• BMNH Natural History Museum, London, England (Maxwell Barclay and Malcolm Kerley).

• CEAH Coleção Entomológica “Adolph Hempel”, São Paulo, Brazil (Sergio Ide).

• CEMT* Coleção Entomológica de Mato Grosso Eurides Furtado, Cuiabá, Brazil (Fernando Vaz-de-Mello).

• CERPE* Coleção Entomológica da Universidade Federal Rural de Pernambuco, Recife, Pernambuco, Brazil (Paschoal Grossi).

• CEUA Colección Entomológica Universidad de Antioquia, Medellín, Colombia (Martha Wolff).

• CMNC Canadian Museum of Nature, Ottawa, Canada (François Génier).

• DZUP* Coleção Entomológica Padre Jesus Santiago Moure, departamento de Zoologia, Universidade Federal do Paraná, Curitiba, Brazil (Lucia Massutti de Almeida).

• ECC Colección Escarabajos Coprófagos de Colombia, Bogotá, Colombia (Alejandro Lopera Toro).

• GHC Gonzalo Halffter collection, Instituto de Ecología, A.C., Xalapa, Veracruz, Mexico (Gonzalo Halffter^† and Fernando Escobar).

• IAvH-E* Instituto de Investigación de Recursos Biológicas Alexander Von Humboldt, Villa de Leyva, Boyacá, Colombia (Jhon César Neita and Edwin Torres).

• ICN-MHN Instituto de Ciencias Naturales-Museo de Historia Natural, Bogotá, Colombia (Germán Amat^†,Fernando Fernández and Juan Botero).

• IRSN Institute Royal de Science de Belgique, Brussels, Belgium (Alain Drumont).

• LCPLC Luis Carlos Pardo-Locarno collection, Palmira (Valle), Colombia (Luis Carlos Pardo-Locarno).

• LUOMUS Luonnontieteellinen keskusmuseo, Finnish Museum of Natural History, University of Helsinki, Finland (Jaakko Matila).

• MACN Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”, Buenos Aires, Argentina (Juan José Martínez and Mario Cupello).

• MAPA Museu Anchieta, Porto Alegre, Brazil (Fernando R. Meyer).

• MFNB Museum für Naturkunde Berlin, Leibniz-Institut für Evolutions und

• Biodiversitätsforschung, Berlin, Germany (Johannes Frisch, Joachim Willers, Eva Sprecher and Gabriel Biffi).

• MHNNKM Museo de Historia Natural Noel Kempff Mercado, Colección entomológica, Santa Cruz de la Sierra, Bolivia (Julieta Ledezma and Marcelo Amaya).

• MLU Martin-Luther-Universität Halle-Wittenberg, Halle-Wittenberg, Germany (Karla Schneider).

• MNHN Muséum National d′Histoire Naturelle, Paris, France (Olivier Montreuil and Antoine Mantilleri).

• MUSM Museo de Historia Natural Universidad Mayor de San Marcos, Lima, Peru (Mabel Alvarado and Luis Figueroa).

• MZLU Lund Museum of Zoology, Stockholm, Sweden (Christoffer Fägerström and Roy Danielsson).

• MZSP* Museu de Zoologia da Universidade de São Paulo, São Paulo, Brazil (Sonia Casari and Carlos Campaner).

• NHMB Naturhistorisches Museum, Basel, Switzerland (Matthias Borer).

• NMNH National Museum of Natural History, Washington, USA (Terry Erwin, material provided by Trond Larsen).

• OUMHN Hope Entomological Collection, Oxford University Museum of Natural History, Oxford, United Kingdom (Darren Mann).

• SMTD Staatliches Museum für Tierkunde, Dresden, Germany (Olaf Jäger and Klaus-D. Klass).

• TAMU Texas A&M University, College Station, TX, USA (Mario Cupello)

• UFPR* Coleção didática Universidade Federal do Paraná, Curitiba, Brazil (Paschoal Grossi).

• UPTC-CE* Colección entomológica de referencia Museo de Historia Natural “Luis Gonzalo Andrade” Universidad Pedagógica y Tecnológica de Colombia, Tunja, Boyacá, Colombia (Juan Carvajal and Irina Morales).

• UVGC Colección entomológica Universidad del Valle de Guatemala, Guatemala, Guatemala (Jack Schuster^† and Enio Cano^†).

• ZSM Zoologische Staatssammlung München, Munich, Germany (Michael Balke and Lars Hendrich).

Species identification was performed using identification keys and original descriptions, as well as by examining all type specimens (Linnaeus, 1767; Olivier, 1789; Ljungh, 1799; Germar, 1823; Say, 1835; Castelnau, 1840; Blanchard, 1846; Erichson, 1848; Guérin-Méneville, 1855; Lucas, 1859; Harold, 1867, 1869, 1875, 1880; Taschenberg, 1870; Burmeister, 1874; Felsche, 1901, 1910, 1911; Waterhouse, 1891; Gillet, 1911; Arrow, 1913; Luederwaldt, 1922, 1923, 1925, 1929, 1935; Pereira, 1942a, 1942b, 1954; Martínez, 1947, 1956, 1974; Landin, 1955; Pereira and Martínez, 1969; Martínez and Martínez, 1982; Kohlmann and Solís, 1997; Génier, 2000; Peraza and Deloya, 2006; Gandini and Aguilar, 2009; Sarmiento-Garcés and Amat-García, 2014; Rossini and Vaz-de-Mello, 2020; Boilly and Vaz-de-Mello, 2021; Chamorro et al., 2021).

The dissection and preparation of the male genitalia (aedeagus) followed the methodology of Zunino (1978). Photographs of the structures of the external and internal morphology of males and females were taken using a Leica motorized stereomicroscope system model M205C with image capture system MC190 HD. Body measurements and scale bars were traced using Leica software. Terminology for external morphology follows Vaz-de-Mello et al. (2011), Lawrence et al. (2010) (mainly for the pterothorax and abdomen) and Nunes and Vaz-de-Mello (2019). Terminology of tegmen follows Nunes and Vaz-de-Mello (2019). The nomenclature of the male genitalia mainly follows the proposal of Tarasov and Solodovnikov (2011), with the following exceptions: the term “endophallite” proposed by Génier (2019) replacing “sclerite”. The term “medial endophallite” replaces “lamella copulatrix” (Medina et al., 2013, modified by Cupello et al., 2022).

Two identification keys are presented, the first to separate Dichotomius from related genera and subgenera, including emendetions to Maldaner et al.’s (2018) and Nunes and Vaz-de-Mello’s (2019) subgeneric diagnoses (shown in bold in the text). The second key is for the species groups of Dichotomius. The definition of each species group and its composition, as well as a description of its known distribution based on Morrone et al.’s (2022) biogeographic regionalization of Latin America, are provided. For the incertae sedis species, the taxonomic treatment includes the following information: Type specimen location, nomenclatural history, material examined, male and female redescription, comments, and geographic distribution. Distribution maps were created in Quantum GIS (QGis version 3.16.8-Hannover). For the type material examined, information on labels was transcribed ipsis litteris. The characteristics of the type labels are described in front of the label information in braces (e.g. {printed text on red label}) and additional information for the labels in square brackets (e.g. [Brazil]). For the additional specimens, the information was organized as follows: country name in capital letters and bold (e.g., BRAZIL), state/department/province name in bold (e.g., Paraná), and the other information in the original language of the label. The number of males (♂) and females (♀) examined is followed by the text of the label. Finally, the entomological collection in which they are housed is given in square brackets after each label description (e.g. [CEMT]). If there is a comma (“,”) in the material examined, it means that it has the same data as the previous one, only modified in this information.

Note: The taxa proposed in this paper are based on years of study of external and internal morphology (not just of the subgenus that is the focus of the study) to help organise Dichotomius and to help clarify the alpha taxonomy of the group. We are aware taxonomic proposals are currently expected to be supported by a formal phylogenetic analysis and that our lack of one may raise objections. We agree with these criticisms, but want to clarify that our proposals are aimed mainly at making identification easier and so path the way to a future phylogenetic classification. The taxa proposed here should be understood, as in any other revision, as hypotheses to be tested in the light of new evidence and interpretations (for an extended discussion, see: Cupello and Vaz-de-Mello, 2018).

List of abbreviations: ME: medial endophallite; SRP: Superior-right peripheral endophallite; FLP: Fronto-lateral peripheral endophallite; A+SA complex: Endophallites of the axial and subaxial complex.

Results and discussion

The division proposed by Luederwaldt (1929) was for many years the main tool in the taxonomy of the genus Dichotomius. Characteristics of the male genitalia have shown greater consistency than intraspecific characteristics of external morphology for defining distinct groups in Scarabaeoidea (Zunino, 1983; d’Hotman and Scholtz, 1990; Zunino and Monteresino, 1990; Cristóvão and Vaz-de-Mello, 2021). In Dichotomius, in the last decade, several studies have found inconsistencies in the groups proposed by Luederwaldt (1929), especially when male genital characters are included; it is therefore concluded that some groups are polyphyletic and have been corrected in recent taxonomic revisions (Arias-Buriticá and Vaz-de-Mello, 2019, 2023, 2024a, 2024b; Nunes and Vaz-de-Mello, 2013, 2019; Rossini and Vaz-de-Mello, 2020; Valois et al., 2017, 2023; Valois et al., 2022).

In this study, we update the classification of Dichotomius sensu stricto based on external morphology and male sexual organ characters. Our analysis concludes: (1) The species Dichotomius triangulariceps (Blanchard, 1846), which has consistently been classified under the subgenera Dichotomius s. str., is now reclassified under the subgenus Selenocopris on the basis of its male genital organ characters, which are similar to those found in other groups of Selenocopris species, mainly in the shape of the parameres and the subgenital plate (Cassenote et al., 2020; Montoya-Molina and Vaz-de-Mello 2021; Valois et al., 2017, 2023; Valois et al., 2022), and the secondary sexual dimorphism of the sixth abdominal ventrite (see the diagnosis of the subgenus Selenocopris). In this subgenus, this species will form the new Dichotomius triangulariceps species group, which, in addition to this species, will be formed by two new species. This group is recognized for having males with a long conical cephalic process in the clypeus and females with a triangular head and a bicuspid process in the frons; in addition to the ME that is asymmetrical and elongated.

(2) The species belonging to the Dichotomius semiaeneus species group, together with four species previously in the subgenus Selenocopris: Dichotomius belus (Harold, 1880), Dichotomius fornicatus (Luederwaldt, 1931b), Dichotomius rafanunezi Montoya-Molina & Vaz-de-Mello, 2021, and Dichotomius subaeneus (Castelnau, 1840) are herein transferred to Dichotomius (Luederwaldtius) Arias-Buriticá & Vaz-de-Mello, new subgenus, and

(3) Dichotomius s. str. has 12 species groups that are defined here, along with two species incertae sedis, Dichotomius agesilaus (Waterhouse, 1891) and Dichotomius compressicollis (Luederwaldt, 1929), which are reviewed in this paper (Table 1).

Table 1
Summary of the taxonomic position of the species under study in this work.

Species	Previous position of the species		Species sensu Arias-Buriticá & Vaz-de-Mello, 2024
	Subgenus	Species group	Subgenus	Species group
Dichotomius adrastus (Harold 1875)	D. (Dichotomius)	mormon sensu Luederwaldt (1929)	D. (Dichotomius)	D. satanas species group
Dichotomius agesilaus (Waterhouse, 1891)	D. (Dichotomius)	mormon sensu Luederwaldt (1929)	D. (Dichotomius)	incertae sedis
Dichotomius alutaceus (Felsche 1901)	D. (Dichotomius)	semiaeneus sensu Pereira (1942)	D. (Luederwaldtius)	D. semiaeneus species group
Dichotomius alyattes (Harold, 1880)	D. (Dichotomius)	mormon sensu Luederwaldt (1929)	D. (Dichotomius)	D. satanas species group
Dichotomius amicitae Kohlmann & Solis, 1997	D. (Dichotomius)	carolinus sensu Kohlmann & Solis (1997)	D. (Dichotomius)	D. carolinus species group
Dichotomius andresi Sarmiento & Amat, 2014	D. (Dichotomius)	mormon sensu Sarmiento & Amat (2014)	D. (Dichotomius)	D. satanas species group
Dichotomius angustus (Luederwaldt, 1929)	D. (Dichotomius)	mormon sensu Luederwaldt (1929)	D. (Dichotomius)	D. satanas species group
Dichotomius annae Kohlmann & Solis, 1997	D. (Dichotomius)	carolinus sensu Kohlmann & Solis (1997)	D. (Dichotomius)	D. carolinus species group
Dichotomius anthrax (Felsche, 1901)	D. (Dichotomius)	semiaeneus sensu Pereira (1942)	D. (Luederwaldtius)	D. semiaeneus species group
Dichotomius australis (Luederwaldt, 1931)	D. (Dichotomius)	semiaeneus sensu Pereira (1942)	D. (Luederwaldtius)	D. semiaeneus species group
Dichotomius belus (Harold, 1880)	D. (Selenocopris)	agenor sensu Montoya-Molina & Vaz-de-Mello (2021)	D. (Luederwaldtius)	D. semiaeneus species group
Dichotomius bicornis (Waterhouse, 1891)	D. (Dichotomius)	mormon sensu Luederwaldt (1929)	D. (Dichotomius)	D. diabolicus species group
Dichotomius bitiensis (Gillet, 1911)	D. (Dichotomius)	bitiensis sensu Pereira (1942)	D. (Dichotomius)	D. bitiensis species group
Dichotomius boreus (Olivier, 1789)	D. (Dichotomius)	boreus sensu Luederwaldt (1929)	D. (Dichotomius)	D. boreus species group
Dichotomius bos (Blanchard, 1846)	D. (Dichotomius)	anaglypticus sensu Luederwaldt (1929)	D. (Dichotomius)	D. bos species group
Dichotomius buqueti (Lucas, 1857)	D. (Dichotomius)	buqueti sensu Arias-Buriticá & Vaz-de-Mello (2019)	D. (Dichotomius)	D. buqueti species group
Dichotomius camargoi Martínez, 1956	D. (Dichotomius)	carolinus sensu Martínez (1956)	D. (Dichotomius)	D. carolinus species group
Dichotomius camposeabrai Martinez, 1974	D. (Dichotomius)	bitiensis sensu Arias-Buriticá & Vaz-de-Mello (2012)	D. (Luederwaldtius)	D. semiaeneus species group
Dichotomius carinatus (Luederwaldt, 1925)	D. (Dichotomius)	boreus sensu Luederwaldt (1929)	D. (Dichotomius)	D. boreus species group
Dichotomius carolinus (Linnaeus, 1767)	D. (Dichotomius)	carolinus sensu Luederwaldt (1929)	D. (Dichotomius)	D. carolinus species group
Dichotomius coenosus Erichson, 1848	D. (Dichotomius)	carolinus sensu Luederwaldt (1929)	D. (Dichotomius)	D. carolinus species group
Dichotomius colonicus (Say, 1835)	D. (Dichotomius)	carolinus sensu Luederwaldt (1929)	D. (Dichotomius)	D. carolinus species group
Dichotomius comarapensis Génier, 2000	D. (Dichotomius)	semiaeneus sensu Génier (2000)	D. (Luederwaldtius)	D. semiaeneus species group
Dichotomius compressicollis (Luederwaldt, 1929)	D. (Dichotomius)	bitiensis sensu Luederwaldt (1929)	D. (Dichotomius)	incertae sedis
Dichotomius conicollis (Blanchard, 1846)	D. (Dichotomius)	mormon sensu Luederwaldt (1929)	D. (Dichotomius)	D. mormon species group
Dichotomius costaricensis (Luederwaldt, 1935)	D. (Dichotomius)	bitiensis sensu Pereira (1942)	D. (Dichotomius)	D. bitiensis species group
Dichotomius cotopaxi (Guérin-Méneville, 1855)	D. (Dichotomius)	cotopaxi sensu Arias-Buriticá & Vaz-de-Mello (2013)	D. (Dichotomius)	D. cotopaxi species group
Dichotomius crenatipennis (Blanchard, 1846)	D. (Dichotomius)	semiaeneus sensuLuederwaldt (1929) as synonym of D. semiaeneus	D. (Luederwaldtius)	D. semiaeneus species group
Dichotomius depressicollis (Harold, 1867)	D. (Dichotomius)	mormon sensu Luederwaldt (1929)	D. (Dichotomius)	D. depressicollis species group
Dichotomius diabolicus (Harold, 1875)	D. (Dichotomius)	mormon sensu Luederwaldt (1929)	D. (Dichotomius)	D. diabolicus species group
Dichotomius divergens (Luederwaldt, 1929)	D. (Dichotomius)	mormon sensu Luederwaldt (1929)	D. (Dichotomius)	D. satanas species group
Dichotomius dynastus Gandini & Aguilar, 2009	D. (Dichotomius)	mormon sensu Gandini & Aguilar (2009)	D. (Dichotomius)	D. diabolicus species group
Dichotomius fornicatus (Luederwaldt, 1931)	D. (Selenocopris)	agenor sensu Montoya-Molina & Vaz-de-Mello (2021)	D. (Luederwaldtius)	D. semiaeneus species group
Dichotomius gandinii Rossini & Vaz de Mello, 2020	D. (Dichotomius)	mamillatus sensu Rossini & Vaz-de-Mello (2020)	D. (Dichotomius)	D. mamillatus species group
Dichotomius haroldi (Waterhouse, 1891)	D. (Dichotomius)	buqueti sensu Arias-Buriticá & Vaz-de-Mello (2019)	D. (Dichotomius)	D. buqueti species group
Dichotomius horridus (Felsche, 1911)	D. (Dichotomius)	reclinatus sensuArias-Buriticá & Vaz-de-Mello (2019, 2023)	D. (Dichotomius)	D. reclinatus species group
Dichotomius latilobatus Boilly & Vaz-de-Mello, 2021	D. (Dichotomius)	bitiensis sensu Boilly & Vaz-de-Mello (2021)	D. (Dichotomius)	D. bitiensis species group
Dichotomius longiceps (Taschenberg, 1870)	D. (Dichotomius)	carolinus sensu Luederwaldt (1929)	D. (Dichotomius)	D. carolinus species group
Dichotomius luctuosioides (Luederwaldt, 1922)	D. (Dichotomius)	semiaeneus sensu Pereira (1942)	D. (Luederwaldtius)	D. semiaeneus species group
Dichotomius mamillatus (Felsche, 1901)	D. (Dichotomius)	mamillatus sensu Rossini & Vaz-de-Mello (2020)	D. (Dichotomius)	D. mamillatus species group
Dichotomius maya Peraza & Deloya, 2006	D. (Dichotomius)	carolinus sensu Peraza & Deloya (2006)	D. (Dichotomius)	D. carolinus species group
Dichotomius melzeri (Luederwaldt, 1922)	D. (Dichotomius)	mormon sensu Luederwaldt (1929)	D. (Dichotomius)	D. depressicollis species group
Dichotomius monstrosus (Harold, 1875)	D. (Dichotomius)	cotopaxi sensu Arias-Buriticá & Vaz-de-Mello (2013)	D. (Dichotomius)	D. cotopaxi species group
Dichotomius mormon (Ljungh, 1799)	D. (Dichotomius)	mormon sensu Luederwaldt (1929)	D. (Dichotomius)	D. mormon species group
Dichotomius motai (Pereira, 1942)	D. (Dichotomius)	bitiensis sensu Pereira (1942)	D. (Dichotomius)	D. bitiensis species group
Dichotomius nemoricola (Pereira, 1942)	D. (Dichotomius)	bitiensis sensu Pereira (1942)	D. (Luederwaldtius)	D. semiaeneus species group
Dichotomius nevermanni (Luederwaldt, 1935)	D. (Dichotomius)	carolinus sensu Luederwaldt (1935)	D. (Dichotomius)	D. carolinus species group
Dichotomius nimuendaju (Luederwaldt, 1925)	D. (Dichotomius)	reclinatus sensuArias-Buriticá & Vaz-de-Mello (2019, 2023)	D. (Dichotomius)	D. reclinatus species group
Dichotomius nitidissimus (Waterhouse, 1891)	D. (Dichotomius)	semiaeneus sensu Pereira (1942)	D. (Dichotomius)	D. bitiensis species group
Dichotomius nutans (Harold, 1867)	D. (Dichotomius)	buqueti sensu Arias-Buriticá & Vaz-de-Mello (2019)	D. (Dichotomius)	D. buqueti species group
Dichotomius ohausi (Luederwaldt, 1923)	D. (Dichotomius)	mormon sensu Luederwaldt (1929)	D. (Dichotomius)	D. mormon species group
Dichotomius pelamon (Harold, 1869)	D. (Dichotomius)	boreus sensu Luederwaldt (1929)	D. (Dichotomius)	D. boreus species group
Dichotomius planicollis (Gillet, 1911)	D. (Dichotomius)	mormon sensu Luederwaldt (1929)	D. (Dichotomius)	D. satanas species group
Dichotomius podalirius (Felsche, 1901)	D. (Dichotomius)	boreus sensu Luederwaldt (1929)	D. (Dichotomius)	D. boreus species group
Dichotomius prietoi Martínez & Martínez, 1982	D. (Dichotomius)	boreus sensu Martínez & Martínez (1982)	D. (Dichotomius)	D. boreus species group
Dichotomius protectus (Harold, 1867)	D. (Dichotomius)	mormon sensu Luederwaldt (1929)	D. (Dichotomius)	D. satanas species group
Dichotomius punctatostriatus (Felsche, 1901)	D. (Dichotomius)	semiaeneus sensu Vulcano et al. (1976)	D. (Luederwaldtius)	D. semiaeneus species group
Dichotomius puncticollis (Luederwaldt, 1935)	D. (Dichotomius)	semiaeneus sensu Luederwaldt (1935)	D. (Luederwaldtius)	D. semiaeneus species group
Dichotomius quadrilobatus Chamorro et al., 2021	D. (Dichotomius)	boreus sensu Chamorro et al. (2021)	D. (Dichotomius)	D. boreus species group
Dichotomius quadrinodosus (Felsche, 1901)	D. (Dichotomius)	reclinatus sensuArias-Buriticá & Vaz-de-Mello (2019, 2023)	D. (Dichotomius)	D. reclinatus species group
Dichotomius quinquedens (Felsche, 1910)	D. (Dichotomius)	mormon sensu Luederwaldt (1929)	D. (Dichotomius)	D. satanas species group
Dichotomius quinquelobatus (Felsche, 1901)	D. (Dichotomius)	mormon sensu Luederwaldt (1929)	D. (Dichotomius)	D. satanas species group
Dichotomius rafanunezi Montoya-Molina & Vaz-de-Mello, 2021	D. (Selenocopris)	agenor sensu Montoya-Molina & Vaz-de-Mello (2021)	D. (Luederwaldtius)	D. semiaeneus species group
Dichotomius reclinatus (Felsche, 1901)	D. (Dichotomius)	reclinatus sensuArias-Buriticá & Vaz-de-Mello (2019, 2023)	D. (Dichotomius)	D. reclinatus species group
Dichotomius ribeiroi (Pereira, 1954)	D. (Dichotomius)	cotopaxi sensu Arias-Buriticá & Vaz-de-Mello (2013)	D. (Dichotomius)	D. cotopaxi species group
Dichotomius robustus (Luederwaldt, 1935)	D. (Dichotomius)	mamillatus sensu Rossini & Vaz-de-Mello (2020)	D. (Dichotomius)	D. mamillatus species group
Dichotomius rugatus (Luederwaldt, 1935)	D. (Dichotomius)	cotopaxi sensu Arias-Buriticá & Vaz-de-Mello (2013)	Synonym of D. monstrosus	NA
Dichotomius rugosicollis (Luederwaldt, 1935)	D. (Dichotomius)	bitiensis sensu Pereira (1942)	D. (Dichotomius)	D. bos species group
Dichotomius satanas (Harold, 1867)	D. (Dichotomius)	mormon sensu Luederwaldt (1929)	D. (Dichotomius)	D. satanas species group
Dichotomius semiaeneus (Germar, 1824)	D. (Dichotomius)	semiaeneus sensu Pereira (1942)	D. (Luederwaldtius)	D. semiaeneus species group
Dichotomius subaeneus (Castelnau, 1840)	D. (Selenocopris)	agenor sensu Montoya-Molina & Vaz-de-Mello (2021)	D. (Luederwaldtius)	D. semiaeneus species group
Dichotomius talaus (Erichson, 1847)	D. (Dichotomius)	mormon sensuLuederwaldt (1929) as synonym of D. conicollis	D. (Dichotomius)	D. mormon species group
Dichotomius texanus (Felsche, 1901)	D. (Dichotomius)	semiaeneus sensu Pereira (1942)	D. (Luederwaldtius)	D. semiaeneus species group
Dichotomius triangulariceps (Blanchard, 1846)	D. (Dichotomius)	mormon sensu Luederwaldt (1929)	D. (Selenocopris)	D. triangulariceps species group
Dichotomius virescens (Luederwaldt, 1935)	D. (Dichotomius)	semiaeneus sensu Pereira (1942)	D. (Luederwaldtius)	D. semiaeneus species group
Dichotomius worontzowi (Pereira, 1942)	D. (Dichotomius)	mamillatus sensu Rossini & Vaz-de-Mello (2020)	D. (Dichotomius)	D. mamillatus species group
Dichotomius zikani (Luederwaldt, 1922)	D. (Dichotomius)	mormon sensu Luederwaldt (1929)	D. (Dichotomius)	D. depressicollis species group

Key to genera and subgenera of the tribe Dichotomiini

(* subgenus with a second key to determine the species group)

1. Antenna with eight antennomeres (Fig. 1a)....................2

   

   Figure 1
   Variable characters in Dichotomiini. Chalcocopris hesperus. a) Antenna. b) Head, pronotum and prolegs dorsal view. Holocephalus eridanus. c) Antenna. Dichotomius (Dichotomius) boreus. d) Antenna. Dichotomius (Homocanthonides) smaragdinus. Male: e) Head and thorax dorsal view. f) Visible abdominal ventrites. Female: g) Head, pronotum and prolegs dorsal view. h) Visible abdominal ventrites. Scale bars: a, c-d = 1 mm; b, e-h = 2 mm.
   

   • 1’. Antenna with nine antennomeres (Figs. 1c, d)....................3

2. Posterior margin of pronotum bordered (Figs. 1e, g; 2a, c; 3a, c, e, g). Seventh elytral interstria flat. Color black, at most with weak blue iridescent sheen. Northern Argentina, Brazil, Peru....................Isocopris Pereira & Martínez, 1960 (see: Rossini and Vaz-de-Mello, 2017; Arias-Buriticá et al., 2023)

   • 2’. Posterior margin of pronotum not bordered (Fig. 1b). Seventh elytral interstria basally convex. Color shiny black or brownish to green metallic. Argentina, Brazil, Paraguay....................Chalcocopris Burmeister, 1846 (see: Rossini and Vaz-de-Mello (2015))

3. Antennal club more or less spherical (Fig. 1c). Second labial palpomere very large, flattened, oval, concealing smaller third palpomere in ventral view. Brazil, Paraguay...Holocephalus Hope, 1838 (See: Smith and Génier (2001); Nunes and Vaz-de-Mello (2016a))

   • 3’. Antennal club elongate (Fig. 1d). Second labial palpomere triangular, not covering the third palpomere in ventral view. United States to Argentina...Dichotomius Hope, 1838....................4

4. Clypeal margin with single medial tooth (Fig. 1e, g). Brazil....................Dichotomius (Homocanthonides) Luederwaldt, 1929 (see: Maldaner et al., 2018)

   • 4’. Clypeal margin rounded, feebly, emarginate or bidentate....................5

5. Head margin at the end of the fronto-clypeal sulcus with invagination giving the appearance of being divided (Fig. 4a, c, e). Metaventrite lacking pilosity (if present, clypeus not distinctly bidentate) (Fig. 4b, d). Small to medium size (less to 20 mm) (Fig. 4a-d)....................Dichotomius (Luederwaldtius) Arias-Buriticá & Vaz-de-Mello, new subgenus

   

   Figure 4
   Characteristics of subgenus Dichotomius (Luederwaldtius) Arias-Buriticá & Vaz-de-Mello, new subgenus. Dichotomius semiaeneus. Male: a) Dorsal view. b) Ventral view. e) Clypeo-genal suture. f) Protibial spur. Aedeagus: g) Lateral view, h) Dorsal view, i) Ventral view. Endophallites: j) SRP, k) A+SA complex, l) FLP. m-n) ME. Female: c) Dorsal view. d) Ventral view. Scale bars: a-d = 2 mm; e-n = 1 mm.
   

   • 5’. Head margin at the end of the fronto-clypeal sulcus lacking invagination, giving it a continuous appearance (Figs. 2a, c; 3a, c, e, g). Metaventrite with pilosity on its entire surface, or at least on the metaventrite lateral side, usually short and scattered, long or rarely absent. Small to large size (more than 11 mm)....................6

     

     Figure 2
     Characteristics of subgenus Dichotomius sensu stricto. Dichotomius boreus. Male: a) Head, pronotum and prolegs dorsal view. b) Visible abdominal ventrites. Female: c) Head, pronotum and prolegs dorsal view. d) Visible abdominal ventrites. Dichotomius mamillatus. e) Male genital organ and endophallus morphology. Scale bars: a-b = 5 mm; c-d = 2 mm; e = 1 mm.
     

6. Clypeal margin rounded or weakly emarginated (Fig. 2a, c). Males sixth abdominal ventrite with constriction at the medial portion (Fig. 2b). United States to Argentina....................Dichotomius (Dichotomius) Hope, 1838*

   • 6’. Clypeal margin distinctly bidentate, teeth usually marginate (Fig. 3a, c, e, g). Males sixth abdominal ventrite with different combination (Fig. 3b, f)....................7

     

     Figure 3
     Dichotomius (Selenocopris) nisus. Male: a) Head and pronotum dorsal view. b) Visible abdominal ventrites. Female: c) Head and pronotum dorsal view. d) Visible abdominal ventrites. Dichotomius (Cephagonus) sp. Male: e) Head and pronotum dorsal view. f) Visible abdominal ventrites. Female: g) Head and pronotum dorsal view. h) Visible abdominal ventral view. Scale bars: a, c, e, g = 5 mm; b, d, f, h = 2 mm.
     

7. Head margin lacking clypeo-genal angle (Fig. 3a, c). Clypeal and genal margin curved (Fig. 3a, c). Ventral clypeal process with truncate or bifurcated apex. Males sixth abdominal ventrite strongly grooved all along with its extension (Fig. 3b). Females sixth ventrite not modified medially (without tubercles, rounded lobes or projections) (Fig. 3d). Mexico to Argentina.............Dichotomius (Selenocopris) Burmeister, 1846 (See: Nunes and Vaz-de-Mello 2016b)

   • 7’. Head margin with clypeo-genal angle (Fig. 3e, g). Clypeal or genal external border straight (Fig. 3e, g). Ventral clypeal process transversely carinate, strongly bifurcate at apex. Males sixth abdominal ventrite lacking strong groove all over its extension (Fig. 3f) (Present in D. ascanius species-group and D. vargasae but these species have the clypeo-genal angle well defined). Females sixth ventrite with modifications at medial area (such as tubercles, rounded lobes or projections) (Fig. 3h). Panama to Argentina..............Dichotomius (Cephagonus) Luederwaldt, 1929 (See: Nunes & Vaz-de-Mello 2019)

Notes on subgenera taxonomy

Recently, Nunes and Vaz-de-Mello (2019), reviewed the nomenclature of the subgenera of Dichotomius and introduced new diagnoses for them. We add some notes on these diagnoses, and establish the new subgenus Dichotomius (Luederwaldtius) Arias-Buriticá & Vaz-de-Mello for a species group previously placed in Dichotomius s. str. and some species of the subgenus Selenocopris:

Dichotomius (Cephagonus) Luederwaldt, 1929

Type species:Pinotus fissus Harold, 1867, designated by Nunes and Vaz-de-Mello (2019)

Diagnosis: distinguished from other subgenera of Dichotomius by the following combination of characters: Clypeus with two acute and conspicuous teeth (Fig. 3e, g). Clypeal or genal external border straight, without division (Fig. 3e, g). Ventral clypeal process transversely carinate, strongly bifurcate at apex. Protibiae inner angle acute or spiniform. Males with sixth abdominal ventrite with constriction at the medial portion (Fig. 3f). Females sixth abdominal ventrite bearing modifications at medial portion (tubercles, lobe or emarginations) and/or pygidium swollen (Fig. 3h). Parameres lacking or having basal and longitudinal excavations; subgenital plate present in ventral view, apex and base round, acute and/or emarginated; base, at junction with phalobase, produced in a membranous excavation or sclerotised– if sclerotised, having grooves or excavations. Panama to northern Argentina (modified from Nunes and Vaz-de-Mello (2019)).

Dichotomius (Homocanthonides) Luederwaldt, 1929

Type species:Copris smaragdinus Perty, 1830; by original monotypy.

Diagnosis: this subgenus is distinguished from others by the following combination of characters: Body with a green metallic. Clypeal margin with central single rounded tooth on clypeal margin (Fig. 1e, g). Ventral clypeal process pronounced into a small tubercle, not bifurcated. Clypeo-genal junction with division and lacking angulation (Fig. 1e, g). Ventral thoracic ventrites glabrous. Sixth abdominal ventrite of females not differentiated by the presence of tubercles, lobe or emarginations (Fig. 1f, g). Parameres lacking excavations, apex elongated; subgenital plate reduced, weakly sclerotized. ME with a square-shapedand with dorsal projection. Brazilian Cerrado (Mato Grosso, Mato Grosso do Sul, Goiás, Distrito Federal, Maranhão, Minas Gerais and São Paulo states) (modified from Maldaner et al., 2018).

Dichotomius (Selenocopris) Burmeister, 1846

Type species:Copris bicuspis Germar, 1823, subsequent designation of Martínez (1951)

Diagnosis: separated from other subgenera by the following combination of characters: Clypeal teeth present, more or less strong (Fig. 3a, c). Clypeal or genal external border lacking clypeo-genal angle or division (Fig. 3a, c). Clypeal and genal margin curved. Ventral clypeal process obtuse, quadrangular or bifurcated. Ventral thoracic ventrites with long dense setae. Female sixth abdominal ventrite three times to four times larger than the fifth ventrite, not modified medially (Fig. 3d). Parameres lacking longitudinal excavations, with subtriangular and slender shape in lateral view, well sclerotized; with subgenital plate short and well esclerotized. ME with subquadrangular to assymetrical shape. Mexico to Argentina (modified from Nunes and Vaz-de-Mello (2019)).

Dichotomius (Luederwaldtius) Arias-Buriticá & Vaz-de-Mello, new subgenus

Type species:Copris semiaeneus Germar, 1823, present designation.

Etymology: The new subgenus is named after Hermann Luederwaldt (1865–1934), a German entomologist who contributed to the taxonomy of many groups of the Scarabaeoidea, especially that of the genus Dichotomius. Furthermore, in his work “As espécies brasileiras do genero Pinotus” (Luederwaldt, 1929), he erected the “Secção Semiaeneus”, for Dichotomius s. str., mentioning that “Aqui attinentes as espécies mais simples e menores: O tronco do genero” (Here are the simplest and smallest species: The base of the genus). This section is in part taxonomically equivalent to our new subgenus.

Diagnosis: The species included in this subgenus are distinguished from other subgenera of Dichotomius by the following combination of characters: Head margin at the end of the fronto-clypeal sulcus with an invagination giving the appearance of being divided (Fig. 4a, c, e). Metaventrite lacking pilosity (if present, clypeus not distinctly bidentate apically) (Fig. 4b, d). Small to medium size (less than 20 mm).

Description: Small size to medium size (less than 20 mm) (Fig. 4). Body shiny or dull black, dark blue or dull green, copper. Clypeus smooth to distinctly bidentate (Fig. 4a, c). Head with processes located in the fronto-clypeal region, simple, conical to lamellate or tridentate in males, conical to tridentate in females. Lateral margin of the head at clypeo-genal junction with division (invagination giving the appearance of being divided), and lacking angulation (Fig. 4a, c, e). Pronotum without pronotal processes at most with a depression on the anterior area (except in males of Dichotomius camposeabrai, which have a strong central excavation) (Fig. 4a, c). Metaventrite without pilosity (if present, clypeus not distinctly bidentate) (Fig. 4b, d). Protibial spur slightly to abruptly angle downward near the apex (Fig. 4f) (in D. subaeneus, bifurcate). Elytral striae well-defined and bicarenate, with small foveate punctures, shallowly impressed and spaced by two to three times their diameter (Fig. 4a, c). Meso- and metalegs with basitarsus from subquadrangular to quadrangular. Pygidium either completely marginated or without margin at the apex. Parameres subtriangular in lateral view and with subgenital plate in ventral view (Fig. 4g-i). ME large and subquadrangular with two well sclerotized processes on the right lateral side, the surface covered with bristles along its entire length, and on the left side it presents a membranous process with long bristles (Fig. 4l-m) (Arias-Buriticá and Vaz-de-Mello (2012, 2019)). Colombia to central Argentina.

Composition:Dichotomius alutaceus (Felsche 1901), D. anthrax (Felsche, 1901), D. australis (Luederwaldt, 1931b), D. camposeabrai Martinez, 1974, D. comarapensis Génier, 2000, D. crenatipennis (Blanchard, 1846), D. luctuosioides (Luederwaldt, 1922); D. nemoricola (Pereira, 1942a), D. punctatostriatus (Felsche, 1901), D. puncticollis (Luederwaldt, 1935), D. semiaeneus (Germar, 1823), D. texanus (Felsche, 1901), D. virescens (Luederwaldt, 1935), D. belus (Harold, 1880), D. fornicatus (Luederwaldt, 1931b), D. rafanunezi Montoya-Molina & Vaz-de-Mello, 2021, and D. subaeneus (Castelnau, 1840) (the last four previously in the subgenus Selenocopris), and some undescribed species, the revision of this subgenus is underway (Arias-Buriticá and Vaz-de-Mello in prep.)

Dichotomius (Dichotomius) Hope, 1838*

Type species:Scarabeus boreus Olivier, 1789, by original designation

Diagnosis: distinguished from other subgenera of Dichotomius by the following combination of characters: Medium to large size individuals (more than 15 mm). Clypeus completely rounded or weakly emarginate, lacking clypeal teeth or inconspicuous (Fig. 2a, C). Head margin at clypeo-genal junction lacking angle or division (Fig. 2a, c). Ventral clypeal process with conical to triangular shape with truncate, bicuspid or acute tip. Metaventrite with long setae on its entire surface, or at least on the metaventrite lateral side. Males with sixth abdominal ventrite with constriction at the medial portion (Fig. 2b). Females sixth abdominal ventrite without constriction and not differentiated by the presence of tubercles, lobe or emarginations (Fig. 2d). Male genital organ with symmetrical parameres, with subtriangular to subquadrangular shapes in lateral view, long parameres with different shapes among species groups (Fig. 2e), with or without subgenital plate, and with or without setae in apical region. Endophallus with tubular shape (Fig. 2e). Medial area of endophallus with semisclerotized membranes with raspules. Four endophallites: ME large and sclerotized, with variable shapes in the species groups (five different shapes) (Fig. 2e). SRP with “C” shape with different widened and sclerotized in the species groups. FLP with “N” shape (Fig. 2e). A+SA complex elongated, curved and with different shapes in the species groups (Fig. 2e). Northeastern United States to central Argentina.

* Key to the species groups of Dichotomius (Dichotomius) Hope, 1838

Note: Before starting to use this key, determine the sex of your specimen. For this, look at the sixth abdominal ventrite: if with constriction at medial portion, it is a male (Fig. 2b), and without such a constriction, it is a female (Fig. 2d).

1. Both sexes with convex pronotum, at most with two very weak and transverse concavities on the anterior side or antero-medial region with a longitudinal depression and two distinct and obtuse lobes on the superior side (Figs. 5d, 8a, b, 17a, b, 25a-c).................2

   

   Figure 5
   Characteristics of Dichotomius bitiensis species group. Dichotomius bitiensis. Male: a) Dorsal view. e) Protibial spur. f) Ventral clypeal process. g) Pygidium. Aedeagus: h) Lateral view, i) Dorsal view, j) Ventral view. Endophallites: k) SRP, l) A+SA complex, m) FLP. n) ME. Female: b) Dorsal view. Dichotomius motai. Male: c) Head and pronotum dorsal view. Dichotomius nitidissimus. Male: d) Head and pronotum dorsal view. Scale bars: a-d = 2 mm; e-n = 1 mm.
   
   

   Figure 8
   Characteristics of Dichotomius bos species group. Dichotomius bos. Male: a) Dorsal view. c) Ventral clypeal process. d) Protibial spur. e) Pygidium. Aedeagus: f) Lateral view, g) Dorsal view, h) Ventral view, i) Apical region of parameres. Endophallites: j) SRP, k) A+SA complex, l) FLP. m) ME. Female: b) Dorsal view. Scale bars: a-b = 5 mm; c-l = 1 mm.
   
   

   Figure 17
   Characteristics of Dichotomius mamillatus species group. Dichotomius mamillatus. Male: a) Dorsal view. c) Ventral clypeal process. d) Protibial spur. e) Pygidium. Aedeagus: f) Lateral view, g) Dorsal view, h) Ventral view. Endophallites: i) SRP, j) A+SA complex, k) FLP. l) ME. Female: b) Dorsal view. Scale bars: a-b = 5 mm; c-l = 1 mm.
   
   

   Figure 25
   Lectotype of Dichotomius compressicollis (Luederwaldt, 1929). a) Dorsal view. b) Labels.
   

   • Both sexes with strong excavation or processes on antero-medial region of the pronotum.................5

2. Fronto-clypeal region of both sexes with a transverse carina that is higher in males (Figs. 5d, 26a, c).................3

   

   Figure 26
   Dichotomius compressicollis. Male: a) Dorsal view. c) Meso-metaesternal suture. d) Ventral clypeal process. e) Protibial spur. f) Pygidium. Aedeagus: g) Lateral view, h) Dorsal view, i) Ventral view. Endophallites: j) SRP, k) A+SA complex, l) FLP. m) ME. Female: b) Dorsal view. Scale bars: a-b = 5 mm; c-m = 1 mm.
   

   • Fronto-clypeal region of both sexes with a conical horn or with two small tubercles in the middle (Figs. 8a, b, 17a, b).................4

3. Black color (Figs. 25a, 26a, c). Mid-lateral pronotal fovea shallow. Male pronotum with posterior-lateral projections directed backwards giving a triangular appearance (Figs. 25a, 26a). Elytral striae shallow to distinctly impressed. Males with triangular head (Figs. 25a, 26a) and rounded in females (Fig. 26c). Small size (11.5–15.3 mm). Colombia, Ecuador, Peru (Fig. 24b).............Dichotomius compressicollis (Luederwaldt, 1929) (incertae sedis)

   

   Figure 24
   a) Distribution map of Dichotomius agesilaus. b) Distribution map of Dichotomius compressicollis.
   

   • Reddish brown and shiny color (Fig. 5d). Medio-lateral pronotal fovea deep. Pronotum of both sexes lacking projections (Fig. 5d). Inconspicuous elytral striae. Both sexes with triangular head (Fig. 5d). Medium size (13-17.1mm). Argentina, Bolivia, Paraguay.................Dichotomius nitidissimus (Dichotomius bitiensis species group)

4. Postero-central region of pronotum sulcate (Fig. 8b). Ventral clypeal process with bicuspid tip (Fig. 8c). Parameres with widened subgenital plate (Fig. 8h). Subtriangular parameres in lateral view (Fig. 8f). Parameres with setae in the apex (Fig. 8g, i). ME with subquadrangular shape with a membranous lobe and long lateral arms (Fig. 8m). Natural or exotic grasslands of Bolivia, Brazil, Paraguay, and Argentina (Fig. 9a).............Dichotomius bos species group

   

   Figure 9
   a) Distribution map of Dichotomius bos species group. b) Distribution map of Dichotomius buqueti species group.
   

   • Posterro-central region of pronotum lacking sulcus (Fig. 17a, b). Ventral clypeal process with obtuse tip (Fig. 17c). Parameres with slender subgenital plate (Fig. 17g). Subtriangular parameres in lateral view (Fig. 17e-g). Parameres lacking setae in the apex (Fig. 17e-g). ME with asymmetrical shape (Fig. 17l). Amazonian (Fig. 18a)..............Dichotomius mamillatus species group

     

     Figure 18
     a) Distribution map of Dichotomius mamillatus species group. b) Distribution map of Dichotomius mormon species group.
     

5. Pygidium with incomplete margin apically (Figs. 5g, 10e, 11e, 14e, 23f)............6

   

   Figure 10
   Characteristics of Dichotomius buqueti species group. Dichotomius buqueti. Male: a) Dorsal view. c) Ventral clypeal process. d) Protibial spur. e) Pygidium. Aedeagus: f) Lateral view, g) Dorsal view, h) Ventral view. Endophallites: i) SRP, j) A+SA complex, k) FLP. l) ME. Female: b) Dorsal view. Scale bars: a-b = 5 mm; c-l = 1 mm.
   
   

   Figure 11
   Characteristics of Dichotomius carolinus species group. Dichotomius carolinus. Male: a) Dorsal view. c) Ventral clypeal process. d) Protibial spur. e) Pygidium. Female: b) Dorsal view. Dichotomius colonicus. Male: Aedeagus: f) Lateral view, g) Dorsal view, h) Ventral view. Dichotomius sp. Endophallites: i) SRP, j) A+SA complex, k) FLP. l) ME. Scale bars: a-b = 5 mm; c-l = 1 mm.
   
   

   Figure 14
   Characteristics of Dichotomius depressicollis species group. Dichotomius depressicollis. Male: a) Dorsal view. c) Ventral clypeal process. d) Protibial spur. e) Pygidium. Aedeagus: f) Lateral view, g) Dorsal view, h) Ventral view, i) Apical region of parameres. j) Media-lateral fovea. Endophallites: k) SRP, l) A+SA complex, m) FLP. n) ME. Female: b) Dorsal view. Scale bars: a-b = 5 mm; c-n = 1 mm.
   
   

   Figure 23
   Dichotomius agesilaus. Male: a) Dorsal view. c) Hypomere. d) Ventral clypeal process. e) Protibial spur. f) Pygidium. Aedeagus: g) Lateral view, h) Dorsal view, i) Ventral view. Endophallites: j) SRP, k) A+SA complex, l) FLP. m) ME. Female: b) Dorsal view. Scale bars: a-b = 5 mm; c-m = 1 mm.
   

   • Pygidium with complete margin (Figs. 7e, 13f, 16f, 19e, 22f)...................11

     

     Figure 7
     Characteristics of Dichotomius boreus species group. Dichotomius boreus. Male: a) Dorsal view. c) Ventral clypeal process. d) Protibial spur. e) Pygidium. Aedeagus: f) Lateral view, g) Dorsal view, h) Ventral view. Endophallites: i) SRP, j)A+SA complex, k) FLP. l) ME. Female: b) Dorsal view. Scale bars: a-b = 5 mm; c-l = 1 mm.
     
     

     Figure 13
     Characteristics of Dichotomius cotopaxi species group. Dichotomius cotopaxi. Male: a) Dorsal view. c) Hypomere. d) Ventral clypeal process. e) Protibial spur. f) Pygidium. Aedeagus: g) Lateral view, h) Dorsal view, i) Ventral view. Dichotomius sp. Endophallites: j) SRP, k) A+AS complex, l) FLP. m) ME. Female: b) Dorsal view. Scale bars: a-b = 5 mm; c-m = 1 mm.
     
     

     Figure 16
     Characteristics of Dichotomius diabolicus species group. Dichotomius diabolicus. Male: a) Dorsal view. Dichotomius bicornis. Male: b) Head and pronotum dorsal view. Dichotomius aff. diabolicus. d) Ventral clypeal process. e) Protibial spur. f) Pygidium. Aedeagus: g) Lateral view, h) Dorsal view, i) Ventral view. Endophallites: j) SRP, k) A+SA complex, l) FLP. m) ME. Female: c) Head and pronotum dorsal view. Scale bars: a-c = 5 mm; d-m = 1 mm.
     
     

     Figure 19
     Characteristics of Dichotomius mormon species group. Dichotomius mormon. Male: a) Dorsal view. c) Ventral clypeal process. d) Protibial spur. e) Pygidium. Aedeagus: f) Lateral view, g) Dorsal view, h) Ventral view. Dichotomius conicollis. Endophallites: i) SRP, j) A+SA complex, k) FLP. l) ME. Female: b) Dorsal view. Scale bars: a-b = 5 mm; c-l = 1 mm.
     
     

     Figure 22
     Characteristics of Dichotomius satanas species group. Dichotomius satanas. Male: a) Dorsal view. d) Ventral clypeal process. e) Protibial spur. f) Pygidium. Aedeagus: g) Lateral view, h) Dorsal view, i) Ventral view. Endophallites: j) SRP, k) A+SA complex, l) FLP. m) ME. Female: b) Dorsal view. Dichotomius adrastus. Female: c) Head and pronotum dorsal view. Scale bars: ac = 5 mm; d-m = 1 mm.
     

6. Protibial spur not angled or slightly angled near the apex (Figs. 10d, 11d, 23e)...................7

   • Protibial spur abruptly angled downward near the apex (Figs. 5e, 14d).................10

7. Elytral striae I to V widened apically (Fig. 11a, b).............8

   • Elytral striae not widened apically.............9

8. Both sexes with triangular head. Antero-medial pronotal region with strong excavation. Males with process located in the back region of the head, lamellar and directed backwards (Fig. 10a). Females with four-pointed process in the frons, the two central ones larger. Females pronotal process with two central lobes (Fig. 10a, b). Southern Brazil, Argentina, and Uruguay.............Dichotomius nutans (Dichotomius buqueti species group)

   • Both sexes with oval head. Antero-medial pronotal region excavated (Fig. 11a, b). Males with bicuspid and directed upwards process in fronto-clypeal region, some males with a second process in the clypeus (Fig. 11a). Females with process in the frons with different shapes, if it is four-pointed, the pronotal process with four lobes (Fig. 11b). Northeastern United States to Brazil and Paraguay (Fig. 12a).............Dichotomius carolinus species group

     

     Figure 12
     a) Distribution map of Dichotomius carolinus species group. b) Distribution map of Dichotomius cotopaxi species group.
     

9. Hypomeron without excavation in the anterior area. Male cephalic process located in posterior region of head with lamellar shape directed backward (Fig. 10a). Females with four-pointed process in the frons (the two central ones larger) or similar to that of the male but the central horn very short (Fig. 10b). Antero-medial region with a depression that goes to the pronotal disc and two distinct and obtuse humps on the superior side (Fig. 10a, b). Parameres with setae apically (Fig. 10f-h). Southern and southeastern Brazil, Argentina, and Uruguay (Fig. 9b)...............Dichotomius buqueti species group

   • Hypomeron with excavation in the anterior area (Fig. 23c). Male cephalic process located in the clypeal region with lamellar shape directed upward (Fig. 23a). Females with two-pointed process in the frons (Fig. 23b). Antero-medial region of pronotum with a longitudinal depression and 4 lobes on the upper side (Fig. 23a, b). Males with spine-shaped process over the lateral foveae and excavation of pronotum with two descending carina from lateral lobes. Parameres glabrous apically (Fig. 23g-i). Southern Brazil (Fig. 24a)...............Dichotomius agesilaus (Waterhouse, 1891) (incertae sedis)

10. Medium to large size (17.4–27.3 mm). Both sexes with bidentate cephalic process, in males located in the clypeal region and in females in the fronto-clypeal region (Fig. 14a, b). Pronotal disc with a big central lobe as wide as the head, with triangular to rounded shape; the lobe continues on each side to the lateral region where it forms two minor processes above the lateral fovea (Fig. 14a, b). Mid-lateral fovea elongated and deep, limited by two sinuous subparallel carinae (Fig. 14j). Peru, Bolivia, Brazil, and Argentina (Fig. 15a)................Dichotomius depressicollis species group

    

    Figure 15
    a) Distribution map of Dichotomius depressicollis species group. b) Distribution map of Dichotomius diabolicus species group.
    

    • Small to medium size (12.5–20.2 mm). Both sexes with conical horn or tranverse carinae located in fronto-clypeal region (Fig. 5a-d). Pronotal disc with small and rounded central lobe as less wide than the head wide as the head or with four lobes (Fig. 5a-d). Mid-lateral fovea rounded and shallow, lacking carinae. Costa Rica, Colombia, Venezuela, Suriname, French Guiana, Brazil, Bolivia, and Argentina (Fig. 6a)................Dichotomius bitiensis species group

      

      Figure 6
      a) Distribution map of Dichotomius bitiensis species group. b) Distribution map of Dichotomius boreus species group.
      

11. Lateral pronotal margin emarginated at the level of the mid-lateral fovea (Fig. 16a-c). Elytral interstriae shagreened, opaque (not corrugated) (Fig. 16a). Andes of Peru and Bolivia (Fig. 15b)..............Dichotomius diabolicus species group

    • Lateral pronotal margin not emarginated at the level of the mid-lateral fovea. Elytral interstriae shagreened to smooth, neveropaque...................12

12. Both sexes with two cephalic processes, the first on clypeus, the second on the fronto-clypeal suture (Fig. 7a, b). Pronotum with ocellate punctures on posterior edge, sometimes denser medially (Fig. 2a, b). Colombia, Venezuela, Ecuador, Peru, Bolivia, Brazil, and French Guiana (Fig. 6b)..............Dichotomius boreus species group

    • Both sexes with one or three cephalic processes. Pronotum without ocellate punctures on posterior edge...................13

13. Head, pronotum and in some cases elytra with calluses, acquiring a wrinkled surface (Fig. 13a, b). Hypomeron with shallow to strong excavation in the anterior area (Fig. 13c). High elevations of the Andes (>2,200 m) in Colombia, Ecuador, and Peru (Fig. 12b)................Dichotomius cotopaxi species group

    • Head, pronotum and elytra without calluses, without wrinkled surface. Hypomeron without excavation.............14

14. Pronotum with strong excavation anteromedially that goes to the two third of it, acquiring a U-shaped aspect, some females with process with two central lobes (Fig. 20a-d). Males with three-horned cephalic process, the first one located at the back of the head, conical to lamellar and directed backwards (sometimes very short); the others two horns located at the base of the first horn or separated at the clypeal region (Fig. 20a, b). Females with the same configuration of cephalic horns as the male (the central one may be shorter) or with a process located in the frons with three or four tips (Fig. 20c-d). Colombia, Ecuador, Suriname, French Guiana, Brazil, Bolivia, and Peru (Fig. 21a)...............Dichotomius reclinatus species group

    

    Figure 20
    Characteristics of Dichotomius reclinatus species group. Dichotomius reclinatus. Male: a) Dorsal view. c) Head and thorax lateral view. f) Protibial spur. e) Pygidium. Aedeagus: h) Lateral view, i) Dorsal view, j) Ventral view. Endophallites: k) SRP, l) A+SA complex, m) FLP. n) ME. Dichotomius nimuendaju. Female: c) Head and pronotum dorsal view. Dichotomius quadrinodosus. Female. d) Head and pronotum dorsal view. Male. e) Ventral clypeal process. Scale bars: a-d = 5 mm; e-n = 1 mm.
    
    

    Figure 21
    a) Distribution map of Dichotomius reclinatus species group. b) Distribution map of Dichotomius satanas species group.
    

    • Pronotum excavated anteromedially, but pronotal processes with differently shaped. Males with one cephalic process on clypeus with lamellar shape (Figs. 19a, 22a). Females with conical cephalic process on fronto-clypeal suture (Figs. 19b, 22b, c)...................15

15. Anterior pronotal margin single lobe medially (Fig. 19a), if not evident, head with genal margin with spine-shaped process (Fig. 19a, b). Parameres subtriangular in lateral view (Fig. 19f-h). ME with double fishing hook shape (Fig. 19l). Colombia, Ecuador, Brazil, Peru, Paraguay, and Bolivia (Fig. 18b)................Dichotomius mormon species group

    • Anterior pronotal margin in the anteriormedial region with two lobes medially (Fig. 22a-c). Parameres anvil shape to subquadrangular in lateral view (Fig. 22g-i). ME with “U” shape (Fig. 22m). Mexico, Central America, Colombia, Venezuela, Ecuador, and Peru (Fig. 21b)................Dichotomius satanas species group

Redefinition of the Dichotomius (Dichotomius) Hope, 1838 species groups

1. Dichotomius (Dichotomius) bitiensis ( Gillet,1911 ) species group

Diagnosis: The species of the D. bitiensis species group are recognized by the following combination of characters: (1) small-sized to medium-sized individuals (12.1–20.2 mm). (2) Head oval to subtriangular in males, and subtriangular in females (Fig. 5a-d). (3) Clypeus with inconspicuous clypeal teeth, sometimes not perceptible by the clypeal projection (Fig. 5a-d). Clypeal surface with well-defined transverse wrinkles. (4) Ventral clypeal process conical with obtuse tip (Fig. 5f). (5) Both sexes with a cephalic process in the fronto-clypeal region, which may be a transverse carina, or a conical process with simple or bicuspidtip (Fig. 5a-d). (6) Protibial spur abruptly angle downward near the apex (Fig. 5e). (7) Pronotum from simple and convex at most with two very weak and transversal concavities to strongly excavated with pronotal processes of four humps that can be the two largest central or the four of equal size (Fig. 5a-d). (8) Elytral striae bicarinate, from shallow to distinctly impressed, though the latter with deep punctures along their entire extension. (9) Pygidium with complete or incomplete apical margin and variable surface punctures (Fig. 5g). (10). Aedeagus with subgenital plate, with widened plates (Fig. 5j). (11) Parameres subtriangular in lateral view (Fig. 5h), with short to long setae in the apical area (Fig. 5h-j). (12) ME subquadrangular, semi-sclerotized in the central area and well sclerotized around it, with two projections and two lobes that have raspules on the surface in different extensions that vary among species (Fig. 5n).

Composition: Five valid species: Dichotomius bitiensis (Gillet, 1911), D. costaricensis (Luederwaldt, 1935), D. latilobatus Boilly and Vaz-de-Mello, 2021, D. motai (Pereira, 1942a), D. nitidissimus (Waterhouse, 1891) and one undescribed species.

Geographic distribution: Pacific dominion (Guajira, Sabana and Puntarenas-Chiriquí provinces), Boreal Brazilian dominion (Guianan lowlands and Roraima provinces), South Brazilian dominion (Madeira, Rondônia and Yungas provinces), Chacoan dominion (Cerrado and Chaco provinces), Paraná dominion (Parana forest province), and South American Transition zones (Páramo province) (Fig. 6a).

2. Dichotomius (Dichotomius) boreus ( Olivier, 1789 ) species group

Diagnosis: The species of the D. boreus species group are recognized by the following combination of characters: (1) Medium-sized to large-sized individuals (16.6–27.1 mm). (2) Head oval and twice as wide as it is long (Fig. 7a, b). (3) Clypeus with two inconspicuous clypeal teeth, sometimes imperceptible (Fig. 7a, b). (4) Ventral clypeal process with invagination and then a conical process obtuse or acute tip (Fig. 7c). (5) Both sexes with two cephalic process, the first one located in the clypeal region and the second one in the fronto-clypeal region (Fig. 7a, b). (6) Protibial spur not angled or slightly angled near the apex (Fig. 7d). (7) Pronotum with an excavation in the anterior area that can go from 1/3 to half of it and laterally to more than 2/3 of the pronotum (Fig. 7a, b). (8) Pronotum with central process with different shapes according to the species. (9) Pronotal process with two humps with spine shape above the lateral foveae. (10) Posterior margin of pronotum with ocellate punctures, sometimes denser in the posteromedial area (Figs. 2a, b, 7a, b). (11) Elytral striae bicarinate, shallow to distinctly impressed and with punctate interestriae. (12) Pygidium with complete apical margin and evident punctures (Fig. 7e) (13). Aedeagus lacking subgenital plate (Fig. 7h). (14) Parameres subtriangular in lateral view (Fig. 7f), without setae in the apical area (Fig. 7f-h). (15) ME well sclerotized, large, and asymmetrical (Fig. 7l).

Composition: Six valid species: Dichotomius boreus (Olivier, 1789), D. carinatus (Luederwaldt, 1925), D. podalirius (Felsche, 1901), D. prietoi Martínez & Martínez, 1982, D. pelamon (Harold, 1869), D. quadrilobatus Chamorro et al., 2021, and two undescribed species.

Geographic distribution: Pacific dominion (Sabana province), Boreal brazilian dominion (all provinces), South Brazilian dominion (all provinces), Chacoan subregion Southeastern Amazonian dominion (Xingu-Tapajós province), and South American Transition zones (Páramo province) (Fig. 6b).

3. Dichotomius (Dichotomius) bos ( Blanchard, 1846 ) species group

Diagnosis: The species of the D. bos species group are recognized by the following combination of characters: (1) Medium-sized to large-sized individuals (14–24.7 mm). (2) Head oval, as wide as it is long (Fig. 8a, b). (3) Clypeus without evident clypeal teeth, sometimes inconspicuos (Fig. 8a, b). (4) Ventral clypeal process conical with bicuspid tip (Fig. 8a, b). (5) Both sexes with conical and directed upward cephalic process in fronto-clypeal area (Fig. 8a, b). (6) Protibial spur not angled or slightly angled near the apex (Fig. 8d). (7) Pronotum with anterior-medial region with a transversal depression and two distinct and obtuse lobes on the superior side (Fig. 8a, b). (8) Lateral pronotal foveae circular and deep. (9) pronotal disc with impressed median longitudinal foveae. (10) Striae bicarinate, shallow to distinctly impressed, with shagreened surface and ocellate punctures in its extension. (11) Pygidium with incomplete apical margin and evident punctures (Fig. 8e). (12) Aedeagus with subgenital plate (Fig. 8h). (13) Parameres subtriangular in lateral view (Fig. 8f), with very short setae in the apical area (Fig. 8g, i). (14) ME subquadrangular with two extensions on the right and setae present throughout the surface. (Fig. 8m).

Composition: Two valid species: Dichotomius bos (Blanchard, 1846) and D. rugosicollis (Luederwaldt, 1935), and one undescribed species.

Geographic distribution: Boreal Brazilian dominion (Pará provinces), South Brazilian dominion (Madeira, Rondônia and Yungas provinces), Chacoan subregion Southeastern Amazonian dominion (Xingu-Tapajós province), Chacoan dominion (Cerrado, Caatinga and Chaco provinces), and Paraná dominion (all provinces) (Fig. 9a).

4. Dichotomius (Dichotomius) buqueti ( Lucas, 1859 ) species group

Diagnosis: This species group was revised by Arias-Buriticá and Vaz-de-Mello (2019). The species of the D. buqueti species group are recognized by the following combination of characters: (1) Medium to large-sized individuals (18–37.4 mm). (2) Both sexes with triangular head (Fig. 10a, b). (3) Clypeus in most widely emarginated and flat, with strong transverse wrinkles. (4) Ventral clypeal process conical with obtuse tip (Fig. 10c). (5) Males with lamelliform cephalic process, subquadrangular at the base and ending at the apical conical process directed forward; with a smaller process on each side at the base of the leading edge at the eye (Fig. 10a). (6) Females with a four-pointed process between the eyes (Fig. 10b) (except in D. haroldi which has two small separate processes). (7) Protibial spur without angle near the apex (Fig. 10d). (8) Both sexes with excavated pronotum in anterior third, with two central tubercles, being stronger in males than in females (Fig. 10a, b). (9) Pygidium with incomplete apical margin (Fig. 10e). (10) Basal area of parameres ending in a strong constriction giving the appearance of spina in lateral and ventral views (Fig. 10f, h). (11) Subgenital plate present (Fig. 10h). (12) Parameres subtriangular in lateral view (Fig. 10f), with long setae at apical area (Fig. 10f-h). (13) ME subquadrangular with two extensions on the right and setae present throughout the surface (Fig. 10l).

Composition: Three valid species: Dichotomius buqueti (Lucas, 1859), D. haroldi (Waterhouse, 1891) and D. nutans (Harold, 1867).

Geographic distribution: Chacoan dominion (Chaco and Pampean provinces), and Paraná dominion (Atlantic, Esteros del Iberá and Paraná Forest provinces) (Fig. 9b).

5. Dichotomius (Dichotomius) carolinus ( Linnaeus, 1767 ) species group

Diagnosis: The species of the D. carolinus species group is recognized by the following combination of characters: (1) Large-sized individuals (23.7–32,1 mm). (2) Head long that wide, subtriangular to oval in males and subtriangular in females (Fig. 11a, b). (3) Clypeus without clypeal teeth and with strong and well-defined transverse wrinkles (Fig. 11a, b). (4) Ventral clypeal process conical with obtuse to acute tip (Fig. 11c). (5) Males with one or two cephalic processes; when they have a single process, it is a transverse bicuspid carina or a widened bicuspid horn in the fronto-clypeal region. If they have two in addition to the previous one, another simple one in the clypeus. (6) Females with a four-pointed process between the eyes (Fig. 11b). (7) Protibial spur not angled or slightly angled near the apex (Fig. 11d). (8) Both sexes with excavated pronotum in anterior third, with pronotal disc with a large central lobe as wide as the head, with triangular to rounded shape, the lobe continues on each side to the lateral region where it forms two minor processes on the lateral fovea (Fig. 11a, b). (9) Elytral striae bicarinate shallow to distinctly impressed, with shagreened surface and ocellate punctures. Elytral striae from 1st to 5th widened in the apical area (Fig. 11a, b). (10) Pygidium with incomplete apical margin and evident puncture (Fig. 11e). (11). Aedeagus with subgenital plate (Fig. 11h). (11) Parameres subtriangular in lateral view (Fig. 11f), with very long setae in the apical area (Fig. 11f-h). (13) ME medium to large, subquadrangular with two extensions on the right and setae present throughout the surface. (Fig. 11l).

Composition: Eigth valid species: Dichotomius amicitae Kohlmann & Solis, 1997, D. annae Kohlmann & Solis, 1997, D. camargoi Martínez, 1956, D. carolinus (Linnaeus, 1767), D. coenosus Erichson, 1848, D. colonicus (Say, 1835), D. longiceps (Taschenberg, 1870), D. maya Peraza and Deloya, 2006, and D. nevermani (Luederwaldt, 1935), and one undescribed species.

Geographic distribution: Mexican transition zone (all provinces), Brazilian subregion Mesoamerican dominion (all provinces), Pacific dominion (Chocó-Darién, Guajira, Guatuso-Talamanca, Magdalena, Puntarenas-Chiriquí, Sabana, and Venezuelan provinces), Boreal Brazilian dominion (Guianan Lowlands, Guianan, and Pará provinces), South Brazilian dominion (Madeira, Rondônia, and Yungas provinces), Chacoan subregion Southeastern Amazonian dominion (Xingu-Tapajós province), Chacoan dominion (Cerrado province), Paraná dominion (Araucaria Forest, Atlantic, and Parana Forest provinces), and South American transition zone (Páramo and Puna provinces) in the Neotropical region. This species group reaches to the Nearctic region in the Western subregion (Rocky Mountain dominion, Chihuahuan province) and Alleghany subregion (Escalante et al., 2021) (Fig. 12a).

6. Dichotomius (Dichotomius) cotopaxi ( Guérin-Méneville, 1855 ) species group

Diagnosis: This species group was revised by Arias-Buriticá and Vaz-de-Mello (2024a). The species of the D. cotopaxi species group is recognized by the following combination of characters: (1) Medium to large size (16–34 mm). (2) Males and females with calluses present on head, pronotum and elytra with corrugated appearence (Fig. 13a, b). (3) Genas with acute and outgoing anterior angle (Fig. 13a). (4) Ventral clypeal process conical with truncate or bicuspid tip (Fig. 13d). (5) Hypomere with anterior excavation (shallow in D. ribeiroi) (Fig. 13c). (6) Protibial spur not angled or slightly angled near the apex (Fig. 13e). (7) Pronotum with anterior angles rounded and invagination in the posterior area of the lateral edge (Fig. 13a, b). (8) Elytra with conspicuous striae formed by deep dimples (except in D. cotopaxi where they are absent or smooth and conspicuous only near the base). (9) Basal region of the striae from the first to the fifth with a basal fovea (Fig. 13a, b). (10) elytral interstriae surface with wrinkles that in some species give at corrugated aspect. (11) Pygidium with complete apical margin (Fig. 13f). (12) Parameres subtriangular in lateral view (Fig. 13g), with long setae at apical area (Fig. 13g-i). (13) Subgenital plate present evident in ventral view, being visible in dorsal view in the middle part of the left paramere (Fig. 13i). (14) ME subquadrangular with two extensions and bristles on its surface (Fig. 13m).

Composition: Five valid species: Dichotomius cotopaxi (Guérin-Méneville, 1855), D. germanchoi Arias-Buriticá and Vaz-de-Mello, 2024, D. luederwaldti Arias-Buriticá and Vaz-de-Mello, 2024, D. monstrosus (Harold, 1875), and D. ribeiroi (Pereira, 1954).

Geographic distribution: Pacific dominion (Cauca and Magdalena provinces), South Brazilian dominion (Yungas province), and South American transition zone (Desert, Puna and Páramo provinces) (Fig. 12b).

7. Dichotomius (Dichotomius) depressicollis ( Harold, 1867 ) species group

Diagnosis: The species of the D. depressicollis species group is recognized by the following combination of characters: (1) Medium-sized to large-sized individuals (17.4–27.3 mm). (2) Head oval as long as it is wide (Fig. 14a, b). (3) Clypeus without clypeal teeth and with strong and well-defined transverse wrinkles (Fig. 14a, b). (4) Ventral clypeal process conical with obtuse to acute tip (Fig. 14c). (5) Both sexes with bidentate head process, in males located in the clypeal region and in females in the fronto-clypeal region (Fig. 14a, b). (6) Protibial spur abruptly angle downward near the apex (Fig. 14d). (7) Males and females with excavated pronotum in anterior third, with pronotal disc with a big central lobe as wide as the head, with triangular to rounded shape, the lobe continues on each side to the lateral region where it forms two minor processes over the lateral fovea (Fig. 14a, b). (8) Media-lateral fovea elongated and deep, limited with two sinuous subparallel carinae (Fig. 14j). (9) Elytral striae bicarinate, shallow to distinctly impressed. (10) Pygidium with incomplete apical margin and evident puncture (Fig. 14e). (11) Aedeagus with subgenital plate (Fig. 14h). (12) Parameres subtriangular in lateral view (Fig. 14f), with short setae in the apical area (Fig. 14i). (13) ME medium to large, subquadrangular with two extensions on the right and setae present throughout the surface (Fig. 14n).

Composition: Three valid species: Dichotomius depressicollis (Harold, 1867), D. melzeri (Luederwaldt, 1922) and D. zikani (Luederwaldt, 1922), and five undescribed species.

Geographic distribution: Boreal Brazilian dominion (Pará provinces), South Brazilian dominion (Madeira, Rondônia and Yungas provinces), Chacoan subregion Southeastern Amazonian dominion (Xingu-Tapajós province), Chacoan dominion (Caatinga and Cerrado provinces), and Paraná dominion (all provinces) (Fig. 15a).

8. Dichotomius (Dichotomius) diabolicus ( Harold, 1875 ) species group

Diagnosis: The species of the D. diabolicus species group is recognized by the following combination of characters: (1) Medium-sized individuals with opaque appearance (15.5–20.4 mm). (2) Head oval as long as it is wide (Fig. 16a-c). (3) Clypeus margined with two inconspicous clypeal teeth and with strong and transverse wrinkles (Fig. 16a-c). (4) Ventral clypeal process with triangular appereance with obtuse tip (Fig. 16d). (5) Males with cephalic process on clypeal area from lamellate to conical (Fig. 16a, b) and females with conical to carinate process on fronto-clypeal area (Fig. 16c). (6) Protibial spur not angled or slightly angled near the apex (Fig. 16e). (7) Anterior angles of pronotum acute (Fig. 16a-c). (8) Lateral pronotal margin at the level of the media-lateral fovea with an invagination (Fig. 16a-c). (9) Males and females with strong excavated pronotum in anterior third, with pronotal disc with a large central process with “Y” shape, or one to four points (Fig. 16a-c). (10) Elytral striae bicarinate, shallow impressed. (11) Elytral interstriae shagreened, giving the appearance of opaque (not corrugated). (12) Pygidium with complete apical margin and evident punctures (Fig. 16f). (13) Aedeagus with slender subgenital plate (Fig. 16i). (14) Parameres with subquadrangular shape in lateral view (Fig. 16g) and without setae in the apical region (Fig. 16g-i). (15) ME well sclerotized with two extensions on the right (Fig. 16m).

Composition: Three valid species: Dichotomius bicornis (Waterhouse, 1891), D. diabolicus (Harold, 1875) and D. dynastus Gandini and Aguilar, 2009, and four undescribed species.

Geographic distribution: South Brazilian dominion (Rondônia and Yungas province), and South American transition zone (Puna Province) (Fig. 15b).

9. Dichotomius (Dichotomius) mamillatus ( Felsche, 1901 ) species group

Diagnosis: This species group was revised by Rossini and Vaz-de-Mello (2020). The species of the D. mamillatus species group is recognized by the following combination of characters: (1) Medium-sized to large-sized individuals (13–22 mm). (2) Head oval and twice as long as it is wide (Fig. 17a, b). (3) Clypeus with two evident clypeal teeth, or inconspicous, surface with strong and well-defined transverse wrinkles (Fig. 17a, b). (4) Ventral clypeal process conical with obtuse tip (Fig. 17c). (5) Fronto-clypeal region of both sexes with a conical horn or with two small tubercles at middle with blunt or truncate (Fig. 17a, b). (6) Protibial spur not angled or slightly angled near the apex (Fig. 17d). (7) Pronotum either regularly convex (at most with two very weak and transversal concavities on the anterior side) or antero-medial region with a longitudinal depression and two distinct and obtuse humps on the superior side (Fig. 17a, b). (8) Elytral striae bicarinate, shallow to distinctly impressed, with shallow to distinctly puntures in its extension. (9) Pygidium with complete or incomplete apical margin and evident punctures (Fig. 17e). (10) Aedeagus with slender subgenital plate (Fig. 17h). (11) Parameres subtriangular in lateral view (Fig. 17f), without setae in the apical area (Fig. 17f-h). (12) ME well sclerotized, large and asymmetrical (Fig. 17l).

Composition: Four valid species: Dichotomius gandiniiRossini and Vaz-de-Mello, 2020, D. mamillatus (Felsche, 1901), D. robustus (Luederwaldt, 1935) and D. worontzowi (Pereira, 1942b).

Geographic distribution: Pacific Dominion (Sabana and Trinida Provinces), Boreal Brazilian dominion (all provinces), South Brazilian dominion (all provinces), Chacoan subregion Southeastern Amazonian dominion (Xingu-Tapajós province), Chacoan dominion (Cerrado province), and South American transition zone (Páramo province) (Fig. 18a).

10. Dichotomius (Dichotomius) mormon ( Ljungh, 1799 ) species group

Diagnosis: This species group was revised by Arias-Buriticá and Vaz-de-Mello (2024b). The species of the D. mormon species group are recognized by the following combination of characters: (1) medium-sized to large-sized individuals (11.4–28.5 mm). (2) Head oval and twice as wide as it is long (Fig. 19a, b). (3) Clypeus with two inconspicuous clypeal teeth, sometimes imperceptible (Fig. 19b). (4) Ventral clypeal process with triangular appereance with acute or obtuse tip (Fig. 19c). (5) Males with lamellar process in the anterior region of head (Fig. 19a). (6) Females with conical process in the fronto-clypeal region (Fig. 19b). (7) Protibial spur without angle near apex (Fig. 19d). (8) Pronotum with strong excavation in the anterior area, pronotal disc with processes 2-6 pointed in males and 2-4 pointed in females (Fig. 19a, b). (9) Anterior margin of pronotum behind head with a single lobe (Fig. 19a). (10) Elytral striae bicarinate, shallow to distinctly impressed. (11) Pygidium with complete apical margin and evident punctures (Fig. 19e). (12). Aedeagus with widened subgenital plate (Fig. 19h). (13) Parameres subtriangular in lateral view (Fig. 19f), without setae in the apical region (Fig. 19f-h). (14) ME well sclerotized, large, and asymmetrical (Fig. 19l).

Composition: Five valid species: Dichotomius conicollis (Blanchard, 1846), D. larseni Arias-Buriticá and Vaz-de-Mello, 2024, D. mormon (Ljungh, 1799), D. ohausi (Luederwaldt, 1923), and D. talaus (Erichson, 1847).

Geographic distribution: Boreal Brazilian dominion (Imerí and Napo provinces), South Brazilian dominion (all provinces), and Paraná dominion (Araucaria, Atlantic, Paraná Forest and Southern Espinhaço provinces) (Fig. 18b).

11. Dichotomius (Dichotomius) reclinatus ( Felsche, 1901 ) species group

Diagnosis: This species group was revised by Arias-Buriticá and Vaz-de-Mello (2023). The species of the D. reclinatus species group are recognized by the following combination of characters: (1) Medium to large-sized individuals (17–34.3 mm). (2) Head oval and twice wider than long (Fig. 20a-d). (3) Clypeal margin complete with two smooth and blunt teeth (Fig. 20a-d). (4) Clypeal surface with strong and well-defined transverse wrinkles. (5) Ventral clypeal process with invagination and then a conical process obtuse tip or with reduced conical process near to mouthparts (Fig. 20e). (6) Males head with three horns the first one is central, directed backwards, subcylindrical and blunt-tipped. The others two horns in the clypeus or at the base of the first horn (Fig. 20a, b) (In D. quadrinodosus where the first horn is dorsoventrally flattened or very short (Males 2)). (7) Protibial spur without angle near apex (Fig. 19f). (8) Males pronotum with antero-medial excavation that takes up two-thirds of its length (except in Males 2 of D. quadrinodosus) (Fig. 20a, b). Female′s pronotum with a central excavation similar or less to the males or with a central two-pointed process (Fig. 20c-d). (9) Pygidium with complete apical margin (Fig. 20f). (10) Male genital organ without subgenital plate (Fig. 20i). (11) Widened parameres in lateral view (Fig. 20g), without setae in the apical region (Fig. 20g-i). (12) Parameres in ventral view with straight inner edge, basal region extended to the phallobase and with an excavation beside this projection (Fig. 20i) (except in D. quadrinodosus). (13) ME well sclerotized, large, and asymmetrical (Fig. 20m).

Composition: Four valid species: Dichotomius horridus (Felsche, 1911), D. nimuendaju (Luederwaldt, 1925), D. quadrinodosus (Felsche, 1901) and D. reclinatus (Felsche, 1901).

Geographic distribution: Pacific Dominion (Cauca, Chocó-Darién, Ecuadorian and Magdalena Provinces), Boreal Brazilian dominion (Guianan Lowlands and Roraima provinces), South Brazilian dominion (Madeira and Rondônia provinces), Chacoan subregion Southeastern Amazonian dominion (Xingu-Tapajós province), Chacoan dominion (Cerrado province), and Paraná dominion (Atlantic, Paraná Forest and Southern Espinhaço provinces) (Fig. 21a).

12. Dichotomius (Dichotomius) satanas ( Harold, 1867 ) species group

Diagnosis: The species of the D. satanas species group are recognized by the following combination of characters: (1) Medium-sized to large-sized individuals (15.1–24.6 mm). (2) Head oval and twice as wide as it is long (Fig. 22a-c). (3) Clypeus with two inconspicuous clypeal teeth, sometimes imperceptible (Fig. 22b, c). (4) Ventral clypeal process with triangular appearance with acute to obtuse tip (Fig. 22d). (5) Males with lamellar process in clypeal region (Fig. 22a). (6) Females with conical process in the fronto-clypeal region (Fig. 22b, c). (7) Protibial spur without angle near apex (Fig. 22e). (8) Anterior margin of pronotum just behind the head with two lobes (Fig. 22a-c). (9) Pronotum with strong excavation in the anterior area, pronotal disc with processes of different numbers of tips and shapes (Fig. 22a-c). (10) Elytral striae bicarinate, shallow to distinctly impressed, with shagreened surface and ocellate punctures in its extension. (11) Pygidium with complete apical margin and evident puncture (Fig. 22f). (12) Aedeagus with slender subgenital plate (Fig. 22i). (13) Parameres upward directed and subquadrangular in lateral view (Fig. 22g), without setae in the apical area (Fig. 22g-i). (14) ME well sclerotized and with “U”-shaped (Fig. 22m).

Composition: Ten valid species: Dichotomius adrastus (Harold 1875), D. alyattes (Harold, 1880), D. andresi Sarmiento and Amat, 2014, D. angustus (Luederwaldt, 1929), D. divergens (Luederwaldt, 1929), D. planicollis (Gillet, 1911), D. protectus (Harold, 1867), D. quinquedens (Felsche, 1910), D. quinquelobatus (Felsche, 1901), and D. satanas (Harold, 1867), and at least four or five undescribed species.

Geographic distribution: Mexican transition zone (Chiapas Highlands, Sierra Madre Oriental, and TransmexicanVolcanic belt provinces), Brazilian subregion Mesoameric dominion (Mosquite, Pacific Lowlands, Veracruzan, and Yucatán Peninsule provinces), Pacific Dominion (Cauca, Chocó-Darién, Ecuadorian, Guajira, Guatuso Talamanca, Puntarenas-Chiriquí, Magdalena, Venezuelan, and Western Ecuador provinces), South Brazilian dominion (Rondônia and Yungas provinces), and South American transition zones (Páramo and Puna provinces) (Fig. 21b).

Incertae sedis species of Dichotomius (Dichotomius) Hope, 1838

Dichotomius (Dichotomius) agesilaus (Waterhouse, 1891)

(Figs. 23a-m, 24a)

• Pinotus agesilausWaterhouse, 1891: 362 (original description)

• Pinotus agesilaus: Blackwelder (1944): 206 (citation); Gillet 1911: 59 (citation); Luederwaldt (1929): 32 (key), 37 (diagnosis) 171 (citation), Fig. No 20 (ilustration); Pessôa and Lane (1941): 462 (diagnosis).

• Dichotomius agesilaus: Vaz-de-Mello (2000): 193 (citation).

Material examined: Holotype [♂]: Labels: 1: {handwritten text on white label} Brasilia St Paul / 2: {handwritten text on white label} agesilaus Reiche. Brazil. / 3: {printed text on white label} 6745 / 4: {handwritten text on ligth blue label} 38 / 5: {handwritten text on green label } r / 6: {printed text on rounded white label with red margins} Type / 7: {printed text on red label with black margins} HOLOTYPE [BMNH]. Additional specimens: BRAZIL: Paraná: Curitiba. 1♂ 2 unsexed. [UFPR]. Palmeiras Trav. & PEARSON COL. 19-XII-1952. 1♂. [CEMT]. C[ampina] Grande do Sul BR116 km 68 I-1990 Grossi EJ. 1♀. [CEMT]. Curitiba X-[1]941 Hats. 1♀. [CEMT]. Curitiba 11-V-1938 Claret. 4♂, 1♀. [CEMT]. Ponta Grossa, Parque Estadual de Vila Velha, 27.i.2011, voando ao amanhecer, P. C. Grossi & F.W.T. Leivas. 1 Unsexed. [CERPE]. Curitiba, Cidade Industrial, área de campo limpo, v.2008, 1000m, Grossi, Parizotto & Melo. 1 Unsexed. [CERPE]. Curitiba 5.[19]39 Coleção F. Justus Jor. 1♂. [DZUP]. Curitiba 22-9-[19]67 O.C. Mangili. 1♂. [DZUP]. Jaguaraiva 30-XII-[19]71 F. Ciacomel. 1♂. [DZUP]. P[onta] Grossa 2.[19]42 Coleção F. Justus Jor. 1♂. [DZUP]. Santa Catarina: Campos Novos 27º 23′S 51°12′W 8-II-2013 Lira D. 1♀. [CEMT]. Mafra 800m 4.[19]66. 2♀. [DZUP]. R[io] Vermelho 800m 12.[19]62. 1♂. [DZUP]. São Bento 800m 2.[19]59. 1♂. [DZUP]. São Paulo: Cruzália 11-V-2004 IGO. 1♀. [CEMT].

Diagnosis: This species can be distinguished by the following combination of characters: (1) Hypomeron with anterior excavation (Fig. 23c). (2) Male clypeus with lamellar process directed upward, female with two-pointed process in frons. (Fig. 23a, b). (3) Ventral clypeal process with bicuspid tip (Fig. 23d). (4) Border of gena acute (Fig. 23a, b). (5) Anterior-medial region of pronotum with a longitudinal depression and 4 lobes on the upper side (Fig. 23a, b). (6) Lateral fovea of pronotum larger and deeper with carina on outer margin. (7) Males with spine-shaped process over the lateral foveae of pronotum and two descending carina from lateral lobes of pronotal process. (8) Elytral striae bicarinate with shagreened surface. (9) Pygidium with incomplete apical margin and evident punctures (Fig. 23f). (10) Male genital organ in lateral view with subtriangular and widened parameres and acute apex (Fig. 23g). (11) Subgenital plate present with widened sclerites protruding above parameres (Fig. 23h). (12) ME is large, and subquadrangular with two well sclerotized processes on the right lateral side, the surface covered with bristles along its entire length, and on the left side it presents membranous process with long bristles (Fig. 23m).

Redescription: Males: Length 28.4‒30.1 mm; width 15.9‒17.6 mm. Black and shiny color.

Head: Wider than long with subtriangular shape. Clypeal margin without teeth. Ventral clypeal process with bicuspid tip. Dorsal surface with well-defined margin leading to the genae (Fig. 23a). Clypeal surface strongly wrinkled and with lamellar process directed upward with bicuspid blunt tip (Fig. 23a). Clypeo-genal suture evident in the base with small process. Genae margin acute with surface with wrinkled surface. Frons and posterior area of head with strong wrinkles.

Thorax: Pronotum wider than long. Anterior angles short and curved, surface with wrinkles giving corrugated appearance. Anterior-medial region with a longitudinal depression with surface, covered with strong wrinkles giving small spines appearance, upper side with pronotal process with 4 lobes (Fig. 23a). Lateral fovea of pronotum larger and deeper with carina on outer margin and over with spine-shaped process. Superio-posterior area of pronotum with large and shallow punctures separated by three to four times their diameter. Posterior margin of pronotum with shagreneed surface and small wrinkles. Hypomeron with anterior excavation glabrous, rest of hypomeron surface shagreened, with dense setigerous punctures (Fig. 23c). Prosternum with denser setigerous punctures, setae long. Elytral striae bicarinate with ondulate margin and shagreened surface. Elytral interstriae with shiny surface, with shallow and larger punctures separated by three to four times their diameter. Mesoventrite shagreened, with short setae. Central area with smooth surface. Meso-metaesternal suture evident. Mesanepisternum shagreened with large setigerous punctures separated by less than once their diameter. Metaventrite anterior lobe with glabrous, shiny surface. Anterior area with a concavity. Central area with longitudinal fovea that goes to the posterior margin, bearing wrinkles in lateral margins near to the insertion of coxa. Metaventrite lateral sides with shagreened surface and denser setigerous punctures. Metanepisternum with similar surface to mesanepisternum.

Abdomen: Shiny ventrites with microsculpture and ocellate punctures with scarce setae in the lateral sides. Sixth ventrite strongly narrowed medially. Pygidium shiny with microsculpture; with small and shallow punctures spaced by more than three times their diameter (Fig. 23f). Pygidium with incomplete apical margin (Fig. 23f).

Legs: Protibia with four lateral teeth. Protibial spur not angled or slightly angled near the apex, going to the middle of the fifth tarsomere (Fig. 23e). Meso- and metatibia gradually widened towards apex, outer margin with eight to ten lateral spines, each with long erect setae; dorsal surface with two longitudinal rows of setae, apical side with setae throughout. Mesotibia with two spurs, unequal in length and acute apically. Metatibial spur apically truncate going to the base of the third tarsomere. Meso and metatibia with five tarsomeres, from first to fourth sub-triangular flattened dorsoventrally, inner edge with long continuous erect setae, outer edge with three to four setae, and the apices with tufts of setae. Basitarsomere of meso and metalegs as long as the 2nd and 3rd joined.

Male genital organ: Lateral view of aedeagus with subquadrangular phallobase, basal area with a medium bulge on both sides, apex with a constriction of approximately 115°and a notch on the lower edge. Male genital organ in lateral view with subtriangular and widened parameres, with acute apex (Fig. 23g). Dorsal view with symmetrical, subtriangular parameres. Central area constricted, and widening apically. Apex of parameres curved (Fig. 23h). Ventral view with symmetrical parameres. Subgenital plate present with widened sclerites protruding between parameres (Fig. 23i). Endophallites: ME is large, and subquadrangular with two well sclerotized processes on the right lateral side, the surface covered with bristles along its entire length, and on the left side it presents a membranous process with long bristles (Fig. 23m). A+SA complex with undefined shape, more sclerotized in the central area surrounded by a semi-sclerotized membrane (Fig. 23k). SRP C-shaped, widened and with undefined edges (Fig. 23j). FLP N-shaped very membranous and only a small area on the right margin (Fig. 23l).

Female: Length 28‒32.1 mm; width 15.4‒18.6 mm. Differs from male by presenting a cephalic bicuspid process on fronto-clypeal area (Fig. 23b). Pronotal process located in the first third region similar in shape to males, without spine process over the lateral fovea, with curved process in internal margin of fovea instead (Fig. 23b). Pronotal punctures more evident than in males. Sixth abdominal ventrite not shortened medially.

Distribution and ecology: Parana dominion (Araucaria forest and Paraná provinces). Known only from southern Brazil (São Paulo, Paraná, and Santa Catarina states) (Fig. 24a). It is an uncommon species in entomological collections. Most specimens are old (1990s or earlier), the most recent was collected in 2013. This species is under evaluation for its conservation status by the IUCN Scarabaeinae group (Maldaner et al., in prep).

Taxonomic comments: Based on the external morphology, the shape of the ventral clypeal process and the endophallites, this species is included in Dichotomius (Dichotomius). The structure of the male genitalia and the excavation in anterior area of hypomeron are similar to that of the D. cotopaxi species group, but the external morphology (head, pronotum and elytra lacking calluses) does not allow it to be included in this group. Furthermore, the Medial endophallite found in this species has a unique structure in the subgenus, and does not allow it to be assigned to any Dichotomius (Dichotomius) species group. It is, therefore, considered an incertae sedis species. It may be later be elevated to a monospecific subgenus within Dichotomius, or described as an independent genus.

Dichotomius (Dichotomius) compressicollis (Luederwaldt, 1929)

(Figs. 25a, b, 26a-m, 24b)

• Pinotus compressicollis Luederwaldt, 1929: 125 (original description)

• Pinotus compressicollis: Blackwelder (1944): 207 (citation); Contreras- Gacharná (1951): 222 (citation).

• Dichotomius compressicollis: Escobar (2000): 208 (citation); Medina et al. (2001): 138 (citation); Noriega-Alvarado (2004): 39 (citation); Pulido et al. (2007): 307 (citation); Medina and Pulido (2009): 59 (citation); Krajcik (2012): 91 (citation); Noriega (2012): 4 (citation); Noriega (2015): 182 (citation); Chamorro et al. (2019a): 38, 41 (citation and photography).

• Dichotomius compresicollis (incorrect subsequent spelling): Sarmiento-Garcés and Amat-García (2014): 106 (diagnosis), 110,113 (citation); 123 (photo); Cárdenas-Bautista et al. (2020): 823, 830, 836 (citation).

• Dichotomius (Dichotomius) compressicollis: Chamorro et al. (2018): 104 (citation); Chamorro et al. (2019b): 110 (citation).

Material examined: Lectotype [♂, here designated]: Labels: 1: {printed text on white label} Columbien / 2: {handwritten text on white label} Staudinger 1927 / 3: {printed text on red label with black margins} COTIPO / 4: {handwritten text on white label with black margins} Pinotus compressicollis gree. / 5: {printed text on white label} 17041 / 6: {printed text on white label} 800 [MZSP] (Fig. 25a, b). Paralectotype [♀, here designated]: Labels: 1: {printed text on white label} Columbien / 2: {handwritten text on white label} Staudinger 1927 / 3: {printed text on red label with black margins} COTIPO / 4: {handwritten text on white label with black margins} Pinotus compressicollis gree. / 5: {printed text on white label} 17040 / 6: {printed text on white label} 800 [MZSP]. Additional specimens: COLOMBIA: Boyacá: Santa Maria 4°51′N 73°16′W 850m. Trampa de excremento de cerdo 21.x.2006 Arias, J. Delgado, P. & F. Molano. 1♀. [UPTC]. Caquetá: Florencia Corpoica-macagual 1°37′N 75°36′W 275m Trampa Pitfall iii-iv.2004 Loaiza, Y. 1♀. [UPTC]. Cundinamarca: Medina Miralindo 4°35′33″N 73°23′17″W 550 m II-II-1997 Ex. Hum Escobar F. 2♂ 1♀. [1♂ CEMT, 1♂ 1♀IAvH-E]. Medina Alto del río Gazaunta Vereda Miralindo Q[ebra]da La Ardita. 550m. 4°35′N 73°23′W T1t3 iii.1997 Escobar F. 1♂. [UPTC]. Meta: Cumaral Finca Pavito 510 m XI-2001 colecta nocturna Noriega J. 3♀. [CEMT]. Villavicencio Bosque de Bavaria 4°9′N 73°38′W 550 m Pitfall ex. Hum. Noriega J. 1♂ 1♀. [CEMT]. Puerto López El Naranjal 4°5′14″N 72°57′30″W 220m II-97 Escobar F. 1♀. [IAvH-E]. El Dorado El Porvenir Bosque 3°42′20.64″N 73°32′36.42″W WGS84 336m T ExH 21.VIII.2013 Isaza L. 2♂ 5♀. [IAvH-E]. Rio Duda PNN Tinigua CIEM 2°40′N 74°10′W 350m TEH I.1996 Jiménez I. 1♂. [IAvH-E]. Villavicencio Agrícola El Naranjal carreera a Puerto Colombia 200m 4°2′N 73°15′W Bosque de Vega Trampa de excrement humano 19.x.2009 López D. 1♀. [UPTC]. Putumayo: Puerto Leguizamo Núcleo Santander -0.127852 -74.616468 Forest 190m 01-IX-2019 Martínez, D. E. & Garcia, D. 1 unsexed individual. [IAvH-E], -0,13521 -74,597957 06-IX-2019. 1 unsexed individual. [IAvH-E]. [Valle del Cauca]: S.A. Felipe Ovalle, Q. Ac. 33501. 1♂ 1♀. [CEMT]. ECUADOR: Orellana: Dayuma Plataforma Primavera 300 m 21-XI-2011 Pitfall excremento Hernández C. 1♀. [CEMT]. Francisco de Orellana Rodrigo Borja IAMOE 04-VI-2000 Pitfall heces humanas Dávalos A. 1♀. [CEMT]. Pastaza: Vía Triunfo-Arajuno 13-VI-1998 Barragán A. 1♂. [CEMT]. Sucumbios: Pacayacu Campo Libertador XII-2010 Pitfall excremento Colecta manual Gallo F. 1♂. [CEMT]. PERÚ: Loreto: Río Pucacuro 9779176 N 04322797 W 203 msnm Bosque primario de terraza (tierra firme) 21-XI-2007 Pitfall carroña Moreno C. 1♂. [CEMT], Pitfall heces. 1♂ 1♀. [CEMT].

Diagnosis: This species can be distinguished by the following combination of characters: (1) Males with clypeus projected giving the appearance of a triangular head, females without projection and oval head. (Figs. 25, 26a). (2) Both sexes with transverse carina in the frons (Figs. 25, 26a, b). (3) Both sexes with anterior angles of pronotum curved. (4) Protibial spur without angle near apex (Fig. 26e). (5) Males pronotum with process giving triangular appearance, but anterior area straight and with two projections in posterior area (Figs. 25, 26a), females with simple pronotum (Fig. 26b). (6) Lateral foveae of pronotum shallow in both sexes. (7) Meso-metaesternal suture not evident (Fig. 26c). (8) Elytral striae bicarinate, not deep and with punctures separated by twice their diameter, sometimes inconspicuous in lateral striae. (9) Pygidium with complete apical margin and evident punctures (Fig. 26f). (10) Male genital organ in lateral view with subquadrangular parameres and straight apex (Fig. 26g). (11) Subgenital plate present (Fig. 26I). (12) Shapes of endophallites (Fig. 26j-m).

Redescription: Males: Length 12.4‒14.5 mm; width 7.7‒8.5 mm. Black and shiny color.

Head: Wider than long with subtriangular shape. Anterior margin is projected, clypeal teeth not evident (Figs. 25a, 26a). Clypeal surface strongly wrinkled. Clypeo-genal suture inconspicuous. Genae surface with wrinkles. Frons with transverse carina from 0.2-1mm long, with two lateral tips and curved central area (some specimens straight), surface around the carina without wrinkles but with ellyptic and weak punctures.

Thorax: Pronotum long than wider, with smooth and shiny appearance. Anterior angles long and curved, surface with scarce, shallow punctures (Figs. 25a, 26a). Disc of pronotum with process giving triangular appearance, with anterior area straight and with two projections in posterior area backwards directed (Figs. 25a, 26a). Lateral foveae inconspicuous. Hypomeron with shagreened surface, with ocellate and setigerous punctures separated by less than once their diameter in the anterior and lateral areas, central area is only shagreened and posterior area with ocellate punctures. Prosternum shagreened with setigerous punctures. Elytral striae bicarinate with shallow and ocellate punctures spaced by about twice times their diameter, sometimes inconspicuous in lateral striae. Elytral interstriae with shallow microsculpture giving shiny appearance and without punctures. Mesoventrite shagreened, with short setae. Central area with a smooth surface. Meso-metaesternal suture not evident (Fig. 26c). Mesanepisternum shagreened with large setigerous punctures separated by less than once their diameter. Metaventrite with anterior lobe with microsculpture, shiny and with setae in lateral margins near to the insertion of coxa. Metaventrite sides with shagreened surface and denser setigerous punctures. Metanepisternum with similar surface to Mesanepisternum.

Abdomen: Shiny ventrites with microsculpture and one rows of ocellate punctures in the anterior area becoming two towards the side. Sixth ventrite strongly narrow medially. Pygidium shiny with microsculpture; with small and shallow punctures spaced by more than three times their diameter (Fig. 26f). Pygidium with complete apical margin (Fig. 26f).

Legs: Protibia with four lateral teeth. Protibial spur simple, without angle near apex going to the base of the fourth tarsomere (Fig. 26e). Meso- and metatibia widened gradually towards apex; outer margin with eight to ten lateral spines, each with long erect setae; dorsal surface with two longitudinal rows of setae, apical side with setae throughout. Mesotibia with two spurs, unequal in length and acute apically. Metatibial spur apically truncate going to the base of the third tarsomere. Meso and metatibia with five tarsomeres, the first four sub-triangular, flattened dorsoventrally, inner edge with long continuous erect setae, outer edge with three to four setae, and the apices with tufts of setae.

Male genitalia: Lateral view of aedeagus with subquadrangular phallobase, basal area with a medium bulge on both sides, apex with a constriction of approximately 115°and a notch on the lower edge. Subquadrangular parameres and straight apex (Fig. 26g). Dorsal view with symmetrical parameres with widened basis (Fig. 26h). Central area with a constriction, widening apically. Apex of parameres curved. Ventral view with symmetrical parameres. Subgenital plate presente with small sclerites (Fig. 26i). Endophallites: ME is large, asymmetrical and sclerotized (Fig. 26m). A+SA complex with undefined form, more sclerotized in the central area surrounded by a semi-sclerotized membrane (Fig. 26k). SRP has “C” form, slender and with defined edges (Fig. 26j). FLP has “n” shape with right lateral area sclerotized and left with semi-sclerotized membrane (Fig. 26l).

Female: Length 11.5‒15.3 mm; width 6.7‒8.9 mm. Differs from male by presenting oval head, with clypeus without central projection (Fig. 26b). Head carina is less pronounced (Fig. 26b). Pronotum is simple, convex and without process (Fig 26b). Sixth abdominal ventrite not shortened medially.

Distribution and ecology: Pacific dominion (Sabana province), Boreal Brazilian dominion (Imerí and Napo provinces) and South American transition zone (Páramo province). Known from Amazon and Andean-Amazon piedemont of Colombia (Boyacá, Caquetá, Cundinamarca, Meta, Putumayo and Valle del Cauca departments), Ecuador (Orellana, Pastaza and Sucumbios provinces), and Peru (Loreto department) (Fig. 24b). It is a rare species in entomological collections. Collected from 200 to 1,200 m of altitude. with pitfall traps baited with carrion and human and pig feces.

Taxonomic comments: Based on the external morphology, the shape of the ventral clypeal process and the endophallites, this species is included as Dichotomius (Dichotomius). However, the inconspicuous meso-metaventral suture, exclusive to this species in Dichotomius (also seen in Canthidium), and the subquadrangular, apically truncate parameresdo not allow D. compressicollis to be assigned to any species group and is, therefore, considered an incertae sedis species. It may later be elevated to a monospecific subgenus within Dichotomius, or described as an independent genus.

Acknowledgments

Thanks to all the curators and collaborators of entomological collections cited in the “Materials and methods” section for their support. To Laboratory of Scarabaeoidology (Universidade Federal de Mato Grosso) for the support (Subproject EECBio UFMT/Finep No 01.12.0359.00). To Subproject Peixes de Mato Grosso INCT- Peixes (funded by MCTIC/CNPq No 405706/2022-7). To the reviewers for their comments, especially to Mario Cupello, who helped improve the final version of the manuscript. JAAB is supported by CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico) (166085/2020-0, 441646/2020-4 PROTAX 2021-2025). JAAB thanks Secretaría de Educación de Boyacá for the work license to develop his doctoral study. FZVM is a CNPq PQ1A/2027 and is supported by CNPq (CNPq 313397/2021-0), PPBio and CNPq (248299/2012-3), FAPEMAT/CNPq PRONEM (568005/2014,0147956/2017), and INCT-CENBAM/CNPq. Funding for this work was granted by INCT-CENBAM/CNPq and L’Institut de Systématique, Évolution, Biodiversité (ISYEB, Muséum National d'Histoire Naturelle, Centre National de la recherche scientifique, France, UMR 7205 CNRS/MNHN). In Dresden, thanks to Juares Fuhrmann and Ester Oliveira for their help in taking the photos of type specimens. To Edrielly Carvalho for the revision and photos of material of DZUP. This paper is part of JA Arias-Buritica’s PhD thesis.

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Edited by

• Associate Editor:
  Frederico Salles

Publication Dates

• Publication in this collection
  27 Jan 2025
• Date of issue
  2025

History

• Received
  08 Mar 2024
• Accepted
  21 Nov 2024