Taxonomic revision of the Phanaeus endymion species group (Coleoptera: Scarabaeidae), with the descriptions of five new species

The Phanaeus endymion species group is defined as a lineage of dung beetles distributed from Mexico to Ecuador. The current arrangement of the P. endymion species group includes 18 species (five newly described and three revalidated herein): P. arletteae Arnaud, 2018; P. bravoensis Moctezuma, Sánchez-Huerta & Halffter, 2017; P. chiapanecus sp. nov.; P. edmondsi Moctezuma, Deloya & Halffter, 2019; P. endymion Harold, 1863; P. funereus Balthasar, 1939 stat. rev.; P. halffterorum Edmonds, 1979; P. huichol Moctezuma, Sánchez-Huerta & Halffter, 2017; P. jackenioi sp. nov.; P. malyi Arnaud, 2002; P. olsoufieffi Balthasar, 1939 stat. rev.; P. pacificus sp. nov.; P. panamensis sp. nov.; P. porioni Arnaud, 2001 stat. rev.; P. pyrois Bates, 1887; P. rzedowskii sp. nov.; P. zapotecus Edmonds, 2006; and P. zoque Moctezuma & Halffter, 2017. Phanaeus dionysius Kohlmann, Arriaga-Jiménez & Rös, 2018 syn. nov. is considered as a new junior subjective synonymy of P. zapotecus Edmonds, 2006. Phanaeus blanchardi Olsoufieff, 1924 and P. bothrus Blackwelder, 1944 are junior objective synonyms of P.  olsoufieffi Balthasar, 1939 stat. rev.


Introduction
The Phanaeus endymion species group is a lineage of rainbow scarab dung beetles distributed from Mexico to Ecuador (Edmonds 1994;Edmonds & Zídek 2012;Lizardo et al. 2017). Species within the P. endymion species group are of great ecological importance since most of them are typically associated with Mesoamerican forests (Edmonds 1994(Edmonds , 2003Arellano et al. 2008Arellano et al. , 2013Huerta et al. The beginning of the 21 st century was distinguished by a controversial application of the subspecieslevel taxa in the P. endymion species group (and in the entire genus Phanaeus). Thereby, the subspecies P. endymion porioni Arnaud, 2001 was described from Honduras and Belize (Arnaud 2001), while P. pyrois malyi Arnaud, 2002 was proposed for specimens from the southern Pacific of Costa Rica (Arnaud 2002a). Additionally, Arnaud (2002b) considered P. olsoufieffi and P. funereus as subspecies of P. pyrois, and proposed Olsoufieff's aberrant viridicollis as a valid species (P. viridicollis Olsoufieff, 1924). Subsequently, P. zapotecus Edmonds, 2006 was described from Mexico and included within the P. endymion species group (Edmonds 2006); while P. pyrois malyi was elevated to full species status based on the results of DNA analyses of specimens from Costa Rica (Solís & Kohlmann 2012).
Later, the taxonomy of Phanaeus was updated and the avoidance of the subspecies category was suggested by Edmonds & Zídek (2012). As a consequence, several nomenclatural changes were proposed and resulted in the P. endymion species group sensu Edmonds & Zídek (2012) including four species: P. endymion, P. pyrois, P. halffterorum and P. zapotecus. Phanaeus viridicollis was considered an unavailable name referable to a chromatic morph of P. pyrois: the name viridicollis was originally proposed as an infrasubspecific taxon (aberration), while some doubtful specimens of P. viridicollis were collected from Nicaragua along with the typical P. pyrois (Edmonds & Zídek 2012). Additionally, the following junior subjective synonyms were recognized by Edmonds & Zídek (2012): P. endymion porioni = P. endymion; P. pyrois funereus Balthasar, 1939 = P. pyrois, P. pyrois olsoufieffi Balthasar, 1939 = P. pyrois, and P. pyrois malyi = P. pyrois. Edmonds & Zídek (2012) argued that the taxonomic recognition of P. endymion porioni was not justified by the morphological differences identified by Arnaud (2001). Additionally, they refused to recognize P. malyi as a valid species, because the analysis of Solís & Kohlmann (2012) did not include samples of the Panamanian and South American populations and chromatic morphs of P. pyrois (Edmonds & Zídek 2012).
Traditionally, the taxonomy of the New World genus Phanaeus has relied on the study of the external morphology (Bates 1887;Olsoufieff 1924;Edmonds 1994;Arnaud 2002b;Edmonds & Zídek 2012). Particularly, the secondary sexual features of major males are considered to be reliable for determining species, while the study of the genital structures has been largely neglected (Edmonds 1994;Arnaud 2002b;Edmonds & Zídek 2012). The morphology of the aedeagus is usually not taxonomically informative enough to separate closely related species of Phanaeus (Edmonds 1994;Arnaud 2002b;Price 2005;Moctezuma et al. , 2019. Nevertheless, the structures of the internal sack of the aedeagus have proved to be valuable for the study of the taxonomy of Scarabaeinae dung beetles (Tarasov & Solodovnikov 2011;Medina et al. 2013;Tarasov & Génier 2015).

MOCTEZUMA V. & HALFFTER G., Taxonomy of the Phanaeus endymion species group
Taking into account the incipient study of the genital morphology of Phanaeus to separate closely related species (Price 2005;Manjarres-H. & Molano-R. 2015), a majority of recent studies implemented the examination of the endophallites to identify and describe new species within the P. endymion species group. The description of P. zoque  was the first that relied on the examination and comparison of the external and genital morphology of the male to separate a new species from the typical P. endymion ). Subsequently,  studied the male external and genital morphology of P. bravoensis Moctezuma, Sánchez-Huerta & Halffter, The phylogenetic species concept sensu Wheeler & Platnick (2000) was adhered to, which defines a species as the smallest aggregation of (sexual) populations or (asexual) lineages that are diagnosable by a unique combination of character states. The subspecies-level is avoided for this work, while intraspecific variability of morphology (such as colouration, body size, and integument) is included within variation of the species. We followed the nomenclature proposed by Harris (1979), Edmonds (1994) and Cristóvão & Vaz-de-Mello (2020) for external morphology and that of  for genital morphology, except for the term endophallite (Génier 2019). The subgenus-level is avoided for this study since Phanaeus and Notiophanaeus have been proven to be artificial groups (Price 2007(Price , 2009Gillett & Toussaint 2020), and Notiophanaeus will probably be considered a synonym of Phanaeus in future works.
Type specimens bear determination labels printed on red acid-free paper, indicating the specimen's sex, and whether they are the holotype or paratypes. Label data is given verbatim. The genital structures were soaked with 10% KOH solution for 24 hours at room temperature, then rinsed with 96% ethanol and later with water. These structures were permanently stored in 15 mm glass microvials (BioQuip Products, Inc., Rancho Dominguez, California, USA) with glycerol, and the microvials were pinned under the dissected specimens.

Distribution
Pacific slope of the Andes, south-central Ecuador (Fig. 17).

Remarks
The genital morphology of this species remains unknown. We were not able to personally revise specimens of Phanaeus arletteae. Nevertheless, the external morphology of the holotype and a female paratype were illustrated by Arnaud (2018). We consider that the diagnostic characters provided by Arnaud (2018) are adequate to separate this species from closely related taxa. The commentaries of previous authors confirmed the validity of this species (Martínez & Pereira 1967;Edmonds 1994;Arnaud 2002b;Edmonds & Zídek 2012). Particularly, the morphology of the pronotum of the female is unique within the P. endymion species group. Moctezuma, Sánchez-Huerta & Halffter, 2017 Figs 1A, 15, 18B, 19B Phanaeus bravoensis : 115. Phanaeus bravoensis -Kohlmann et al. 2018: 69. -Moctezuma et al. 2019.

Remarks
This species was recently described by . To the original description we add that the elytral striae are impressed basally as distinct fossae; right lobe of endophallite copulatrix is more developed than left lobe; right lobe of endophallite copulatrix obtusely triangular, arched superiorly; left lobe of endophallite copulatrix lobed, strongly reduced; central ridge more developed than central MOCTEZUMA V. & HALFFTER G., Taxonomy of the Phanaeus endymion species group column (Fig. 1A). For the female, the trituberculate cephalic carina with nearly aligned, similar sized, conical tubercles; frons punctures scarce, almost effaced; pronotal surface distinctly punctate; pronotal process trituberculate with a posterior concavity; all pronotal tubercles rounded, with middle tubercle slightly more developed and projected frontally than lateral tubercles; posterior pronotal midline distinctly impressed.   Edmonds, 2006 (VMC).
tergite Viii. Dark green, scabriculous; with rough, distinctly impressed punctures. Basal margin with setae variable in size.

Major male
Head. Clypeus bidentate, black on anterior margin, dark metallic blue-green or green on posterior portion, rough sculpture. Genae dark metallic blue-green or green with rough sculpture. Front black, with dark metallic blue-green or green on portions adjacent to cephalic horn. Cephalic horn black, curved posteriorly over pronotum (Figs 2B, 4A-B).
Pronotum. Uniformly dark blue, dark metallic blue-green or dark metallic green, becoming black beneath posterolateral angles. Carinate, distinctly developed keel in the middle of anterior pronotal margin, or keel completely effaced. Disc triangular, flat, with two distinctly developed tubercles on anterior portion. Triangle with lightly granulate or nearly smooth sculpture, scabriculous, impunctate. Sides with almost smooth sculpture, scabriculous, with superficially impressed punctures. Lateral lines of triangle straight. Posterolateral angles short, widened, sometimes lightly projected posteriorly. Lateral fossae distinctly impressed. Basal fossae obtusely oval, superficially to deeply impressed. Posterior margin with superficially to deeply impressed punctures (Figs 2B, 4A-B).
elytra. Striae fine, dark metallic blue-green, or dark metallic green, scabriculous, impressed basally as distinct fossae, with distinctly impressed to effaced punctures. If punctures distinctly impressed, each forming a distinct fossa, giving a completely roughened surface to first and second striae. If punctures effaced, interstriae completely smooth. Interstriae black, with smooth surface, scabriculous, superficially impressed to effaced punctation. Sutural margin without apical tooth (Figs 4A-B).
Protibiae. Quadridentate with apical spine. MOCTEZUMA V. & HALFFTER G., Taxonomy of the Phanaeus endymion species group tergite Viii. Dark metallic blue-green, or dark metallic green, scabriculous; with rough, distinctly impressed punctures. Basal margin with setae variable in size.

Minor male
Like the major male, except for the reduction of secondary sexual characters (i.e., cephalic horn, pronotal triangle and tubercles, and pronotal posterolateral angles).

Female
Similar to the male, except for the head showing a cephalic trituberculate carina with similar in size, nearly aligned, conical tubercles; frons with distinctly to superficially impressed punctures; pronotal sculpture completely smooth, with superficially impressed punctures; shining black, variable in size area on central portion of pronotal disc; pronotal process trituberculate, with posterior concavity; middle pronotal tubercle more developed, dentiform or rounded, always more frontally projected than lateral tubercles; lateral tubercles obtusely rounded or carinate; posterior pronotal midline superficially impressed to completely effaced (Fig. 4C).

Variation
Mean length 17.9 mm (13.9-20 mm). The typical colour morph is dark metallic blue-green (Figs 4A, C), but a less frequent dark metallic green morph (Fig. 4B) is also found, while scarce specimens are completely bright metallic green. The interstriae are completely dark metallic blue-green or dark metallic green in some specimens. The rarest specimens from Chiapas and Veracruz show a bright metallic yellow or red sheen on head, pronotum and elytra. Variation in the interstrial punctation is observed in the whole distribution area of P. endymion. The size of the right and left lobes of the endophallite copulatrix is not homogeneous.

Distribution
From Veracruz and the Yucatan Peninsula to Belize and northern Guatemala (Fig. 15).

Remarks
The lectotype (a minor male), a female paralectotype and several specimens (n = 42) from the type locality cited by Harold (1863) were used for the redescription of P. endymion, that was complemented with specimens from its whole distribution area. As a consequence, the high intraspecific variation of P. endymion is adequately represented herein. Although P. endymion is a polymorphic species, closely related species are confidently separated by differences in the pronotal morphology of males and females, elytral interstriae, and genital morphology. Balthasar, 1939 stat. rev. Figs 1E, 2C, 5, 17, 18F, 19F Phanaeus (s. str.) funereus Balthasar, 1939: 241.

Diagnosis
Easily diagnosed species by the dull black colour with dull red sheen dorsally; and striae not strongly impressed basally (Fig. 5). Additionally, the major male with a keel absent in the middle of anterior pronotal margin (Figs 2C, 5A); endophallite copulatrix as Fig. 1E. The major female with the pronotal process lacking concavity; middle pronotal tubercle more developed, slightly projected frontally than lateral tubercles; all pronotal tubercles rounded; and posterior pronotal midline completely effaced (Fig. 5B).
Pronotum. Keel absent in the middle of anterior pronotal margin. Disc triangular, flat; with two elongate, weakly developed tubercles on anterior portion. Triangle dull black, scabriculous, with almost effaced punctures, smooth sculpture. Sides dull black-red; scabriculous, with smooth sculpture, almost effaced punctures. Lateral lines of triangle straight. Posterolateral angles short, slightly widened. Lateral fossae distinctly impressed. Basal fossae absent or almost effaced. Posterior margin with almost effaced punctures (Figs 2C, 5A).
tergite Viii. Dull black, with dark red to dark brown sheen; scabriculous sculpture; rough, distinctly impressed punctures. Basal margin with setae variable in size.
genitalia. Right lobe of endophallite copulatrix larger in size than left lobe. Right lobe obtusely triangular in shape, with superior portion projected frontally. Left lobe lobed inferiorly, bent superiorly. Central ridge less developed than central column (Fig. 1E).

Minor male
Like the major male, except for the attenuation of the secondary sexual characters (i.e., cephalic horn, pronotal triangle and tubercles, and pronotal posterolateral angles; Fig. 5C).

Female
Similar to the male, except for the head showing a cephalic trituberculate carina, with similar in size, conical tubercles; middle tubercle more frontally projected than lateral tubercles; frons with almost effaced punctures; pronotal sculpture completely smooth, impunctate or with almost effaced punctures; pronotum almost completely dull black, dark metallic red laterally and posteriorly; pronotal process trituberculate lacking concavity; middle pronotal tubercle more developed, slightly projected frontally than lateral tubercles; all tubercles rounded; posterior pronotal midline completely effaced (Fig. 5B).

Variation
Mean length 19.3 mm (16-21.9 mm). The male specimen from Colombia has acute posterolateral pronotal angles that are posteriorly projected.

Distribution
Pacific slope of the Andes, north-central Ecuador and Colombia (Fig. 17). The Colombian specimen represents the first record of P. funereus from Colombia.

Type locality
Mexico, State of Mexico, Temascaltepec.

Distribution
Central Trans-Mexican Volcanic Belt, State of Mexico and Morelos (Fig. 15).

Remarks
Mean length 17.4 mm (13.4-19.9 mm). The specimens from Morelos (Deloya et al. 1993) were not studied by us. This species was erroneously reported from Mexico City (Arnaud 2002b). This mistake is attributed to Hinton (1935), who recorded it from Real de Arriba, Mexico D.F. Real de Arriba is actually located in the State of Mexico. Despite the fact that  split P. halffterorum and P. bravoensis, the colouration pattern of P. halffterorum remains as indicated by Edmonds (1979), with bright metallic green or dark metallic blue specimens. In a review of the immature dung beetles of Scarabaeinae (Edmonds & Halffter 1978), the name P. halffterorum Edmonds, 1978 was published. Nevertheless, this may be considered as a nomen nudum under Article 13 of the Code (ICZN 1999). Consequently, the same name was available later for the same or a different concept under Arts 21, 50; while P. halffterorum Edmonds 1979 must be considered the available authorship and date.
To the original description of the male we add that the right lobe of the endophallite copulatrix is more developed than the left lobe; the right lobe ois btusely triangular; the left lobe is obtusely rectangular; the central ridge lis ess developed than the central column (Fig. 1F). For the female can be added that the trituberculate cephalic carina has conical, nearly aligned tubercles; the middle tubercle is more raised than the lateral tubercles; the pronotal process is trituberculate, with a posterior concavity; all the tubercles are rounded; the middle tubercle is slightly more developed and projected frontally than the lateral tubercles; the pronotal midline is distinctly impressed, with superficially impressed punctures; the pronotal surface is smooth, with almost effaced punctures. Moctezuma, Sánchez-Huerta & Halffter, 2017 Figs 1G, 15, 18H, 19H Phanaeus huichol Moctezuma et al., 2017: 123.

Distribution
Sierra Madre Occidental; Jalisco, northern Michoacán, Nayarit and southern Sinaloa (Fig. 15). The first record of P. huichol from Michoacán is presented herein.

Remarks
The original description of P. huichol indicates that the colour pattern varies from dark metallic green, bright metallic green, to dark green with blue sheen. After revising additional specimens, a bright metallic green morph with red sheen was found by us. To the original description we add the elytral striae impressed basally as distinct fossae; and central ridge and column of endophallite copulatrix similar in size (Fig. 1G). For the female, the head showing a cephalic trituberculate carina with middle tubercle more frontally projected, carinate and less prominent than lateral tubercles; frons with almost effaced punctures; pronotal sculpture completely smooth, with almost effaced punctures; pronotal process trituberculate, with posterior concavity, followed posteriorly by reduced, rounded tubercle; middle tubercle dentiform or rounded, more developed and projected frontally than lateral tubercles; lateral tubercles rounded or carinate; posterior pronotal midline completely effaced.

Diagnosis
Easily diagnosed species by the bright metallic green colour; striae wide, roughened, impressed basally as distinct fossae, with distinctly impressed punctation; the major male with posterolateral angles of pronotum sharply acute, elongate, projected posterolaterally (Figs 2D, 6A); the major female with pronotal process without frontal concavity; rounded pronotal tubercles, nearly aligned, with middle tubercle more developed than lateral tubercles (Fig. 6B).

Etymology
We are honoured to dedicate this new species to Jack Schuster and Enio Cano. They have significantly contributed to the knowledge of the Guatemalan scarab beetles, particularly of the family Passalidae.
Head. Clypeus bidentate, black on anterior margin, bright metallic green on posterior portion, with roughened sculpture. Genae bright metallic green, with roughened sculpture. Front black, with dark metallic blue-green on portions adjacent to cephalic horn. Cephalic horn black, curved posteriorly over pronotum (Figs 2D, 6A).
genitalia. Right lobe and left lobe of endophallite copulatrix similar in size. Right lobe obtusely triangular in shape, with apical portion projected posteriorly. Left lobe bent posteriorly, convex superiorly, lobed inferiorly. Central ridge and column similar in size (Fig. 1H).

Minor male
Like the major male, except for the reduction of secondary sexual characters (i.e., cephalic horn, pronotal triangle and tubercles, and pronotal posterolateral angles).

Female
Similar to the male, except for the head showing a cephalic trituberculate carina; carinate middle tubercle, less raised, slightly more frontally projected than lateral tubercles; lateral tubercles obtusely conical; frons with distinctly impressed punctures; pronotal sculpture completely smooth, with superficially impressed punctures; pronotum bright metallic green, with shining black, variable in size area on central portion of disc; pronotal process trituberculate, lacking concavity rounded pronotal tubercles, nearly aligned, with middle tubercle more developed than lateral tubercles; posterior pronotal midline completely effaced (Fig. 6B).

Distribution
Inner slope of the Sierra Madre de Chiapas, south-central Guatemala and southeastern Chiapas (Fig. 15).

Diagnosis
Easily diagnosed species by the bright black colour with red-green sheen on frontolateral angles of pronotum (Fig. 2E); elytral striae fine, smooth, impressed basally as distinct fossae (Fig. 7). The rest of black species within the P. endymion species group (P. funereus, P. olsoufieffi, P. panamensis sp. nov.) are differentiated from P. malyi by the elytral striae not strongly impressed basally as distinct fossae and the shape of the endophallite copulatrix (Fig. 1).

Type material
Holotype (
Pronotum. Keel absent in the middle of anterior pronotal margin. Disc triangular, flat; with two weakly developed, elongate tubercles on anterior portion.  European Journal of Taxonomy 747: 1-71 (2021) tergite Viii. Bright metallic red-green, scabriculous sculpture; with rough, superficially impressed punctures. Basal margin with setae variable in size.
genitalia. Right and left lobes of endophallite copulatrix similar in size. Right lobe obtusely triangular in shape, rounded superiorly. Left lobe obtusely lobed. Central ridge less developed than central column (Fig. 1I).

Minor male
Like the major male, except for the reduction of the secondary sexual characters (i.e., cephalic horn, pronotal triangle and tubercles, and pronotal posterolateral angles).

Female
Similar to the male, except for the head showing a cephalic trituberculate carina, with nearly aligned, rounded or carinate, weakly developed tubercles; middle tubercle slightly more developed than lateral tubercles; frons with superficially impressed punctures; pronotum with almost effaced punctures; pronotal process trituberculate, lacking concavity; middle pronotal tubercle more developed, slightly more projected posteriorly than lateral tubercles; all tubercles rounded in shape; posterior pronotal midline completely effaced to almost effaced (Fig. 7B).

Distribution
Southern Pacific costal area, Costa Rica, Panama and Colombia (Figs 16-17). The specimens revised by us represent the first accurate records of P. malyi from Panama. Apparently, the distributions of P. malyi and P. panamensis sp. nov. show a significant area of sympatry and both species may be collected in the same locality (e.g., Cerro Hornito, Panama). Nevertheless, P. malyi and P. panamensis sp. nov. are confidently identified by the diagnosis provided herein and putative hybrid specimens were not found by us. The MNHN EC10569 specimen represents the first record for P. malyi in Colombia. Nevertheless, the illegible label data prevents us to provide an accurate locality (Fig. 7C). The extent of the distribution of P. malyi in Colombia needs to be confirmed by future research.

Diagnosis
This is the largest species within the P. endymion species group, frequently attaining 21-24 mm in length. Phanaeus olsoufieffi is diagnosed by the black colour with bright metallic red-green sheen; and elytral striae not strongly impressed basally (Fig. 8). This species is easily separated from the closely related P. panamensis sp. nov. by the larger body size and endophallite copulatrix (Fig. 1). Additionally, the major males of P. olsoufieffi are diagnosed by the distinctly developed keel in the middle of anterior pronotal margin; and posterolateral angles rounded, strongly developed, and projected laterally (Figs 2F, 8A).
tergite Viii. Bright metallic red, with green sheen; scabriculous; with rough, superficially impressed punctures. Basal margin with setae variable in size.
genitalia. Right lobe of endophallite copulatrix slightly more developed than left lobe. Right lobe obtusely triangular in shape; weakly developed, projected frontally. Left lobe concave superiorly, lobed inferiorly. Central ridge less developed than central column (Fig. 1J).

Minor male
Like the major male, except for the reduction of secondary sexual characters (i.e., cephalic horn, pronotal triangle and tubercles, and pronotal posterolateral angles).

Female
Similar to the male, except for the head showing a cephalic trituberculate carina; with weakly developed tubercles; carinate middle tubercle, slightly more frontally projected and more developed than lateral tubercles; frons with superficially impressed punctures; pronotal sculpture smooth, with almost effaced to effaced punctures; pronotum almost completely black, becoming posteriorly and laterally bright metallic red with green sheen; pronotal process trituberculate, lacking concavities; pronotal tubercles weakly developed, well-spaced, with middle tubercle more developed and posteriorly projected than lateral tubercles; posterior pronotal midline completely effaced (Fig. 8B).

MOCTEZUMA V. & HALFFTER G., Taxonomy of the Phanaeus endymion species group
Variation Mean length 20.1 mm (15.9-23.9 mm). Minor males occasionally show the pronotal disc almost completely bright metallic red, with green sheen.

Distribution
Pacific Slope of the Andes, north-central Colombia and northern Ecuador (Fig. 17). Previous authors reported P. olsoufieffi from Panama (Arnaud 2002b;Kohlmann et al. 2018). Nevertheless, these authors confused P. olsoufieffi with P. panamensis sp. nov. The specimens revised herein are the first accurate records of P. olsoufieffi from Ecuador. The distributions of P. olsoufieffi and P. funereus show a significant area of sympatry. Nevertheless, we did not find any putative hybrid specimens.

Remarks
Phanaeus olsoufieffi was considered as a synonym of P. pyrois by previous authors (Edmonds 1994;Edmonds & Zídek 2012). Nonetheless, a diagnosis and an updated key to separate P. olsoufieffi and closely related species are provided by us. As a consequence, P. olsoufieffi is confidently resurrected herein from previous synonymy and full species status is assigned to it. The lectotype of P. olsoufieffi is a minor male (Fig. 8C). Therefore, the redescription mainly relies on the type series and some specimens (n = 8) collected from the type locality (Valle del Cauca, Colombia). When revising the type material deposited at MNHM, we were not able to find out the locality data for a Colombian female paralectotype of P. olsoufieffi (MNHN EC10567). Its locality data is probably indicated in an illegible label. Additionally, we found out that a paralectotype of P. olsoufieffi pertained to P. malyi (Fig. 7C, MNHN EC10569). Consequently, we conclude that the type series of P. olsoufieffi lumped together two distinct species. Previous authors (Arnaud 1982;2002a, 2002bEdmonds 1994

Diagnosis
Species typically dark blue or blue-green (Figs 2G,9), easily separated from the closely related by the elytral striae deeply punctate, with each puncture forming a distinct fossa, giving a completely roughened surface to all striae (Fig. 9). Additionally, the major males of P. pacificus sp. nov. and P. jackenioi sp. nov. are distinguished by the carinate keel in the middle of anterior pronotal margin of the former (Fig. 2).

Etymology
The specific epithet refers to the Pacific slope, where the new species occurs.
genitalia. Right and left lobes of endophallite copulatrix similar in size. Right lobe obtusely triangular in shape, concave medially. Left lobe strongly developed, concave posterosuperiorly. Central ridge and column similar in size (Fig. 1K).

Minor male
Like the major male, except for the reduction of the secondary sexual characters (i.e., cephalic horn, pronotal triangle and tubercles, keel on anterior margin, and pronotal posterolateral angles).

Female
Similar to the male, except for the head showing a cephalic trituberculate carina; with conical tubercles; middle tubercle slightly more projected frontally than lateral tubercles; lateral tubercles slightly more raised than middle tubercle; frons distinctly impressed, rough punctures; pronotal sculpture completely smooth, with distinctly impressed punctures; pronotum almost completely dull black in the central portion, dark metallic blue, or blue-green laterally and posteriorly; pronotal process trituberculate, lacking concavities; pronotal tubercles nearly aligned; with rounded to dentiform middle tubercle, more developed than lateral tubercles; posterior pronotal midline superficially impressed (Fig. 9B).

Variation
Mean length 17.1 mm (14.1-20.2 mm). A rare bright metallic green or yellow-green with a red sheen colour morph was found. The smaller males may show a keel weakly developed to completely effaced in the middle of anterior pronotal margin.

Distribution
Pacific slope of the Sierra Madre de Chiapas; Chiapas, Guatemala and El Salvador (Fig. 15).

Diagnosis
The new species is easily diagnosed within the P. endymion species group by the dull black colour with bright metallic red-green sheen dorsally (Figs 2H,10); and elytral striae not strongly impressed basally as distinct fossae (Fig. 10). Phanaeus panamensis sp. nov. is distinguished from P. olsoufieffi by its smaller body size (rarely attaining 20-21 mm in length); and the major males with obsolete keel in the middle of anterior pronotal margin (Fig. 2H); and posterolateral angles weakly developed, widened, slightly projected posteriorly (Fig. 10A). Furthermore, the pronotal disc in P. olsoufieffi is distinctly darker and smoother (Figs 2F, 8A).

Etymology
The specific epithet refers to Panama, where a majority of the type series was collected.
Head. Clypeus bidentate, black on anterior margin, bright metallic red, with green sheen on posterior portion, roughened sculpture. Genae bright metallic red, with green sheen; roughened sculpture. Front black, bright metallic red on portions adjacent to cephalic horn. Cephalic horn black, curved posteriorly over pronotum (Figs 2H, 10A).
tergite Viii. Bright metallic red, with green sheen, scabriculous; with rough, almost completely effaced punctures. Basal margin with thick, small setae.
genitalia. Right lobe of endophallite copulatrix more developed than left lobe. Right lobe obtusely triangular in shape, rounded superiorly, and weakly developed. Left lobe bent posteriorly. Central ridge and column similar in size (Fig. 1L).

Minor male
Like the major male, except for the reduction of the secondary sexual characters (i.e., cephalic horn, pronotal triangle and tubercles, and pronotal posterolateral angles). Occasionally, the pronotal disc is completely bright metallic red, with green sheen.

Female
Similar to the male, except for the head showing a cephalic trituberculate carina; with weakly developed tubercles; carinate middle tubercle, slightly more frontally projected than lateral tubercles; frons with distinctly impressed punctures; pronotal sculpture completely smooth, with superficially impressed punctures; pronotum almost completely dull black in the central portion, laterally and posteriorly bright metallic red with metallic green sheen; pronotal process trituberculate, lacking concavities; pronotal tubercles rounded, nearly aligned, well-spaced; with middle tubercle more developed than lateral tubercles; posterior pronotal midline almost completely effaced (Fig. 10B).

Distribution
Panama and north-Caribbean Costa Rica (Fig. 16). The distributions of P. panamensis sp. nov., P. malyi and P. pyrois show large areas of sympatry. Nevertheless, all these species are easily recognized.

Diagnosis
Phanaeus porioni and P. endymion are closely related, but the former is easily separated by the major female with the pronotal process weakly or not concave posteriorly and pronotal tubercles nearly aligned (Fig. 11B), while the males are distinguished by the endophallite copulatrix (Fig. 1). Additionally, P. porioni is recognized by the elytral striae always distinctly punctate (Fig. 11), but the strial surface never roughened as in P. pacificus sp. nov. (Fig. 9) and P. jackenioi sp. nov. (Fig. 6).
tergite Viii. Dark metallic blue, green, or blue-green; scabriculous; with rough, superficially impressed punctures. Basal margin with setae variable in size.
genitalia. Right and left lobes of endophallite copulatrix similar in size. Right lobe obtusely triangular in shape, weakly developed superiorly. Left lobe obtusely lobed, strongly developed. Central ridge less developed than central column (Fig. 1M).

Minor male
Like the major male, except for the reduction of the secondary sexual characters (i.e., cephalic horn, pronotal triangle and tubercles, and pronotal posterolateral angles).

Female
Similar to the male, except for the head showing a cephalic trituberculate carina; with weakly developed, nearly aligned tubercles; carinate middle tubercle slightly more developed than lateral tubercles; frons with distinctly impressed punctures; pronotal sculpture smooth, with almost completely effaced punctures; pronotum almost completely black, becoming dark metallic blue, green, or blue-green posteriorly and laterally; pronotal process trituberculate, weakly concave posteriorly; pronotal tubercles nearly aligned; with rounded to dentiform middle tubercle, more developed than lateral tubercles; lateral tubercles rounded; posterior pronotal midline almost completely effaced (Fig. 11B).

Remarks
Phanaeus porioni was considered as a synonym of P. endymion by Edmonds & Zídek (2012). Nevertheless, differences in external and genital morphology were found by us. As a consequence, P. porioni is resurrected from previous synonymy and full species status is given to it. Apparently, a significant area of sympatry is found between P. endymion and P. porioni. The males of both species are strongly mimetic, but females are easily diagnosed by external morphology. The endophallite copulatrix will help to confidently separate males of both species (Fig. 1). We were not able to study any specimens of P. porioni from Belize.  Bates, 1887 Figs 1N, 2J, 12, 16, 18O, 19O Phanaeus pyrois Bates, 1887: 58, pl. 2, table 3, figs 22-23 (in part).

Diagnosis
Easily diagnosed species by the pronotum bright metallic red (Figs 12A, D), green (Fig. 2J) or dark metallic blue (12B), with elytral striae not strongly impressed basally (Fig. 12). The rest of the green/ blue species of the P. endymion species group are recognized by the elytral striae strongly impressed basally as a distinct fossa. A black dorsal colour is never found in P. pyrois specimens. Minor males of P. panamensis sp. nov. and red P. pyrois may be strongly mimetic, but easily separated by the endophallite copulatrix (Fig. 1).
tergite Viii. Bright metallic red, green, or dark metallic blue; scabriculous; with rough, superficially impressed punctures. Basal margin with setae variable in size.
genitalia. Right and left lobes of endophallite copulatrix similar in size. Right lobe strongly reduced, obtusely triangular in shape; rounded superiorly. Left lobe obtusely lobed, strongly developed. Central ridge and column similar in size (Fig. 1N).

Minor male
Like the major male, except for the reduction of secondary sexual characters (i.e., cephalic horn, pronotal triangle and tubercles, and pronotal posterolateral angles).

Female
Similar to the male, except for the head showing a cephalic trituberculate carina; with conical, nearly aligned tubercles; middle tubercle slightly more developed than lateral tubercles; frons with distinctly impressed punctures; pronotal sculpture smooth, with almost effaced punctures; pronotum almost completely black, becoming posteriorly and laterally bright metallic red, green, or dark metallic blue; pronotal process trituberculate, lacking concavity; pronotal tubercles nearly aligned; with middle tubercle more developed than lateral tubercles; posterior pronotal midline superficially impressed (Fig. 12C).

Variation
Mean length 17.8 mm (14.7-20.1 mm). Phanaeus pyrois is the most variable in colour species of the P. endymion species group. The outspoken colour variability of this species was previously outlined by Bates (1886Bates ( -1889, particularly for the specimens from Nicaragua. Tree typical chromatic morphs were found by us (bright metallic red, Fig. 14A, D; green, Fig. 2J; or dark metallic blue, Fig. 12B), but colour combinations are found and rare specimens has a bright golden sheen.

Distribution
Nicaragua and north-Caribbean Costa Rica (Fig. 16). The distributions of P. pyrois and P. panamensis sp. nov. show an important sympatry area in north Caribbean Costa Rica.

Remarks
Phanaeus pyrois and several closely related species were incorrectly lumped together by previous authors (Howden & Young 1981;Edmonds 1994 European Journal of Taxonomy 747: 1-71 (2021, 2019GBIF Secretariat 2019b). Differences in body colour and the pronotal, elytral and genital morphology were found to confidently diagnose P. pyrois and all the closely related species. The blue chromatic morph of P. pyrois (Fig. 12B) was suggested by Edmonds (1994) to be a hybrid with P. endymion. Nevertheless, blue specimens of P. pyrois (Fig. 12B) do not share the diagnostic characters with P. endymion (Figs 1D, 2B, 4). As a consequence, there is no evidence to consider a hybridization between P. endymion and P. pyrois. Edmonds & Zídek (2012) suggested that doubtful specimens of "viridicollis" (Figs 2J, 12C) were collected in Nicaragua along with "normal" P. pyrois. After revising the doubtful specimens of "viridicollis" from Nicaragua (Figs 2J, 12C), we disagree with Edmonds & Zídek (2012) and conclude that they incorrectly referred to the green chromatic morph of P. pyrois as P. viridicollis.

Diagnosis
This is the only species within the P. endymion species group where major males show a pronotal disc with a superficially impressed midline (Fig. 2K).

Etymology
We are honoured to name the new species after Jerzy Rzedowski, to recognise his outstanding contribution to the knowledge of the Mexican biodiversity, particularly to the flora from El Bajío region.
tergite Viii. Dark metallic blue-green, scabriculous; with rough, superficially impressed punctures. Basal margin with setae variable in size.
genitalia. Right lobe of endophallite copulatrix more developed than left lobe. Right lobe obtusely triangular in shape, sharply acute frontally, rounded superiorly. Left lobe strongly developed, obtusely lobed. Central ridge more developed than central column (Fig. 1O).

Minor male
Unknown.

Female
Similar to the male, except for the head showing a cephalic trituberculate carina; with almost aligned, conical tubercles, similar in size tubercles; frons distinctly impressed, rough punctures; pronotal sculpture completely smooth, with superficially impressed punctures; colour of pronotum as in P. endymion; pronotal process trituberculate, posteriorly concave; dentiform middle tubercle, strongly developed, more frontally projected than lateral tubercles; almost completely reduced lateral tubercles (Fig. 13B). European Journal of Taxonomy 747: 1-71 (2021) Variation Mean length 17.4 mm (16.5-18.2 mm). Chromatic variation was not observed in the type series.

Phanaeus zapotecus
Phanaeus zapotecus -Edmonds & Zídek 2012: 1, 7-8. -Moctezuma & Halffter 2017: 52, 54-55, fig. 23. -Moctezuma et al. 20172019: 253. Phanaeus (Notiophanaeus) zapotecus - Edmonds & Zídek 2012: 3, 13, figs 139, 141, 143, 148-151. Phanaeus (Notiophanaeus) dionysius -Kohlmann et al. 2018: 68, 70. Non Phanaeus endymion -Edmonds 1994: 44 (referred to as "Oaxaca" population). Non Phanaeus (Notiophanaeus) "Oaxaca" endymion -Edmonds 1994: fig. 221. Paratypes MEXICO -Oaxaca • 2 ♀♀; same collection data as for holotype; IEXA • 1 ♂; "La mesita San Pablo Etla, 14-VII-17, coprotrampa, x-96°44'53.55''O, y-17°9'53.55''N, bosque de Encino, 1954 Kohlmann et al. (2018) recently described P. dionysius based upon specimens from San Pablo Etla, Oaxaca, Mexico and suggested that P. zapotecus and P. dionysius were sister taxa. The following character combination helps to separate both species according to Kohlmann et al. (2018): P. dionysius has long and slender pronotal posterolateral angles, whereas P. zapotecus has short and rounded posterolateral angles. The basal border of the tergite VIII in P. dionysius forms a small indentation at its middle, whereas it runs completely straight in P. zapotecus. Additionally, the apex of the parameres of P. dionysius is more projected, than that from P. zapotecus. Moreover, the middle sinuation of the parameres in lateral view is much more pronounced in P. dionysius. Nevertheless, we consider that the description and diagnosis of P. dionysius exemplify some of the frequent problems occurring in taxonomical work (Komarek & Beutel 2006) as follows. Kohlmann et al. (2018) did not indicate how many specimens of P. zapotecus they revised, but they commented that the paratypes housed at CNIN were checked by them. Taking into account this information and the original description of P. zapotecus (Edmonds 2006), we assume that Kohlmann et al. (2018) revised two paratypes at most. Kohlmann et al. (2018) were not able to adequately assess the morphological variation of P. zapotecus, as a consequence of the reduced number of paratypes studied by them. The pronotal posterolateral angles were found by us to be long and slender in some paratype major males of P. zapotecus (Fig. 14A). The basal border of the tergite VIII is highly variable: four paratypes of P. zapotecus revised by us show the small indentation at the middle of the basal border of the tergite VIII (Fig. 14D), whereas it runs completely straight in two paratypes. The small indentation is present in the basal border of the tergite VIII of three specimens of P. dionysius revised by us, whereas it runs completely straight in two paratypes (Fig. 14E). Kohlmann et al. (2018) illustrated the endophallite copulatrix of P. dionysius (available from https://zookeys.pensoft.net/article/23029/zoom/fig/13/) but they overlooked its comparison with P. zapotecus (Fig. 1P). We noticed that the morphology of both P. zapotecus (Fig. 1P) and P. dionysius is identical when we compared the endophallites under the microscope. Furthermore, the endophallite copulatrix of the holotype of P. dionysius has suffered deformation and abrasion, maybe as a result of the preparation methods (soaking for 5 min in a solution of 5% boiling KOH) and/or storage (dry preservation in a plastic microvial). This structure was not found by us to be stored in a microvial with glycerol as mentioned by Kohlmann et al. (2018). The morphology of the cephalic carina and the pronotal tubercles of the females of P. zapotecus (Fig. 14B) and P. dionysius (see https://zookeys.pensoft.net/article/23029/zoom/fig/14/) did not differ. Moreover, the body colour in the paratypes of P. zapotecus varied from jet black or bright dark blue to jet black with a green-blue sheen ( Fig. 14A-C), falling within the variation of P. dionysius (Kohlmann et al. 2018). Kohlmann et al. (2018) commented that a major male was designated as holotype. Nevertheless, we found out that the holotype of P. dionysius housed at IEXA is the minor male illustrated by Kohlmann et al. (2018) in the original description (available from https://zookeys.pensoft.net/article/23029/zoom/ fig/15/). As a consequence, we assume that the original description of P. dionysius was not based on the holotype. We found that a paratype minor male of P. zapotecus (Fig. 14C) and the holotype of P. dionysius

MOCTEZUMA V. & HALFFTER G., Taxonomy of the Phanaeus endymion species group
Characters not suitable for a study at a given taxonomic rank The revision of a majority of species within the P. endymion species group led us to conclude that the morphology of the aedeagus is not taxonomically informative to separate species, as suggested by previous authors (Edmonds 1994;Price 1995;Arnaud 2002b;Moctezuma et al. , 2019. In the light of the findings presented herein, we conclude that the description and diagnoses provided by Kohlmann et al. (2018) do not justify the splitting of P. dionysius and P. zapotecus in two different species. As a consequence, a new junior subjective synonymy is recognized herein: Phanaeus zapotecus Edmonds, 2006= Phanaeus dionysius Kohlmann, Arriaga-Jiménez & Rös, 2018.

Remarks
Mean length 16.4 mm (14.8-18.5 mm). To the original description of this species, we add that the elytral striae are impressed basally as distinct fossae (Fig. 14); right lobe of endophallite copulatrix more developed than left lobe; right lobe obtusely triangular in shape, strongly developed superiorly; left lobe strongly reduced, lobed, slightly concave inferiorly; central ridge more developed than central column (Fig. 1P). For the female, the head shows a cephalic trituberculate carina; with almost aligned, conical tubercles; middle tubercle slightly more developed than lateral tubercles; frons with almost effaced punctures; pronotal process trituberculate, with posterior concavity; rounded pronotal tubercles; with middle tubercle slightly more developed than lateral tubercles; posterior pronotal midline distinctly impressed (Fig. 14B). Edmonds (2006) commented that the holotype and three paratypes (1 ♂, 2 ♀♀) of P. zapotecus were housed at IEXA. However, the type material was not found by us at IEXA in a recent search. Therefore, the holotype and these paratypes are considered temporarily lost. It is possible that the former collection manager of IEXA, Professor Miguel Angel Morón Ríos, knew the location of the holotype and paratypes of P. zapotecus, but, unfortunately, we were not able to confirm this assumption because of his recent death. Moctezuma & Halffter, 2017 Figs 1Q, 15, 18R, 19R Phanaeus zoque Moctezuma & Halffter, 2017: 47, 48, 52, 55-56, figs 1-15, 23.

Remarks
Mean length 15.8 mm (13.2-18.4 mm). To the original description we add the elytral striae impressed basally as distinct fossae; right and left lobes of endophallite copulatrix similar in size; right lobe obtusely triangular in shape, distinctly rounded superiorly; left lobe strongly developed, obtusely lobed; central ridge less developed than central column (Fig. 1Q). For the female, the head showing a cephalic trituberculate carina; with conical, similar in size tubercles; middle tubercle slightly more frontally projected than lateral tubercles; frons with almost effaced to effaced punctures; pronotal sculpture completely smooth, with almost effaced to effaced punctures; pronotal process trituberculate, with posterior concavity; with dentiform middle tubercle, strongly more developed and projected frontally than lateral tubercles; carinate or rounded lateral tubercles; posterior pronotal midline almost completely effaced.

Discussion
By comparing the external and genital morphology of hundreds of specimens, revisiting the original species descriptions, and examining type material of problematic species (e.g., P. endymion, P. dionysius, P. funereus, P. olsoufieffi, P. porioni, P. pyrois, P. zapotecus), the taxonomy of the P. endymion species group has been reassessed and several taxonomical issues were disentangled. As a consequence, five new species have been described and three previously described species have been resurrected from synonymy. Contrary to previous authors (Edmonds 1994;Edmonds & Zídek 2012;Moctezuma et al. , 2019, who considered that the morphology of the females within the P. endymion species group was relatively homogeneous and taxonomically uninformative, we highlight the importance of the pronotal and cephalic morphology of females to confidently separate closely related species. Furthermore, the morphological variation of females was pivotal in developing a new determination key. Additionally, we found that in the P. endymion species group body colouration and the morphology of the endophallite copulatrix, which have traditionally been neglected in the taxonomy of Phanaeus (Martínez & Pereira 1967;Edmonds 1994;Edmonds & Zídek 2012), can be informative characters. Differences in body colour were accompanied by differences in the external and genital morphology.  Prior studies have demonstrated that at least in some instances, differences in body colouration may be supported by molecular sequence data as demonstrated by Solís & Kohlmann (2012). Since Phanaeus are diurnal beetles, body colour and iridescence are expected to be important for mate choice and visual social signaling directed to conspecifics and predators (Vulinec 1997), while both body colour and iridescence are a result of light absorption and the interference in reflected light rays propagating through micron-sized structures composed of organized nano-sized elements of the beetle cuticles (Michelson 1911;Vargas et al. 2018).
Therefore, we conclude that earlier authors underestimated the usefulness of body colouration to diagnose closely related species within the P. endymion species group (Martínez & Pereira 1967;Edmonds 1994;Edmonds & Zídek 2012), and the microstructures responsible of body colour and iridescence in Phanaeus cuticles might be a new and unexplored source of taxonomic characters. Additionally, the morphology of the endophallite copulatrix was reported to be homogeneous in closely related species of the P. amethystinus, P. quadridens, P. tridens and P. vindex species groups (Price 2005;. However, this is not the case with the P. endymion species group, for which we found a significant interspecific variation in the morphology of the endophallite copulatrix (Fig. 1). The wide genital variety of males might be a driver of diversification within the P. endymion species group, since variation in genital structures is thought to drive a rapid evolutionary divergence in other groups of arthropods (Yao et al. 2020). Nevertheless, further corroboration of our taxonomic conclusions using independent data such as DNA sequences for all relevant taxa would be desirable.
In addition, we consider that the most complete taxonomic treatment for the genus Phanaeus was proposed by Arnaud (2002b), as previously suggested by  for the P. quadridens species group. Nevertheless, Arnaud's (2002b) classification has limitations, such as the use of the subspecieslevel without clear boundaries between species and subspecies. Future revisions of Phanaeus are needed because the species richness of this genus might be dramatically underestimated since Arnaud (2002b) proposed 77 taxa (species and subspecies) and 34 synonyms, while Edmonds & Zídek (2012) recognized only 54 valid species and suggested 53 synonyms.
Consequently, we proposed that the P. endymion species group represented a recent penetration of Neotropical origin that arrived in Mexico during the Plio-Pleistocene climatic fluctuations (Halffter & Morrone 2017;. In this context, P. endymion and P. pyrois were considered as putatively basal taxa, while P. halffterorum, P. zapotecus and P. zoque represented marginal colonizations of montane regions ).
Nevertheless, some considerations arose as follows. The term "basal taxa" does not make sense, because every branching in a phylogenetic tree is rotatable. Consequently, there are always two most basal clades, both originating from a node with equal age and evolutionary change (Krell & Cranston 2004). Additionally, the P. endymion species group is widely distributed in montane regions. The P. endymion species group contains several species associated with tropical rainforests (P. arletteae, P. edmondsi, P. endymion, P. funereus, P. malyi, P. olsoufieffi, P. pacificus sp. nov., P. panamensis sp. nov., P. porioni, P. pyrois), mountain cloud forests (P. endymion) and tropical dry forests (P. arletteae, P. bravoensis, P. chiapanecus sp. nov.). On the other hand, at least seven species inhabit the temperate coniferous-oak forests of Mesoamerica (P. bravoensis, P. halffterorum, P. huichol, P. jackenioi sp. nov., P. rzedowskii sp. nov., P. zapotecus and P. zoque). Apparently, the diversification of the P. endymion species group and its dispersal to the Mexican temperate forests started during the Miocene (Price 2009;Kohlmann et al. 2018;Gillett & Toussaint 2020).
We hypothesize that the P. endymion species group has a significant plasticity to invade new ecological niches. The ecological plasticity of the P. endymion species group is supported by the heterogeneous ecosystems that it inhabits, such as the aforementioned tropical rainforests, tropical dry forests, mountain cloud forests, and temperate coniferous-oak forests (Edmonds 1994(Edmonds , 2003(Edmonds , 2006Moctezuma et al. , 2019. Furthermore, some species may be opportunistic to invade forest borders and tropical pastures, such as P. endymion (Edmonds 1994(Edmonds , 2003Salomão et al. 2020). The invasion of the P. endymion species group to these environments (such as the temperate forests and tropical pastures) might involve the development of adaptations in ecophysiological processes (e.g., respiration and temperature control) to tolerate dryness and microclimatic changes (Chown & Klok 2011;Moctezuma et al. 2016).
On the other hand, the P. endymion species group is the only one within Phanaeus that successfully shifted from coprophagy to necrophagy, mycetophagy and saprophagy (Halffter & Matthews 1966;Edmonds 1994Edmonds , 2003Edmonds , 2006Halffter & Halffter 2009;Deloya et al. 2013;Gillett & Toussaint 2020). A combination of both the evolution of mandible morphology and symbiotic interactions may explain the remarkable trophic generalism of the P. endymion species group. The modifications of mandible morphology are known to be a key factor that allowed the evolution from the saprophagous ancestors to the modern coprophagous Scarabaeinae (Bai et al. 2015), while the effects of digestive symbionts have driven trophic generalism in herbivorous beetles (McKenna et al. 2019;Salem et al. 2020) and are responsible of facilitating digestion and nutrition process in dung beetles (Thiyonila et al. 2018;Suárez-Moo et al. 2020).

MOCTEZUMA V. & HALFFTER G., Taxonomy of the Phanaeus endymion species group
Although our study adhered to the phylogenetic species concept sensu Wheeler & Platnick (2000), we hope that the species described and redescribed herein are compatible with other popular species concepts, such as the biological species concept sensu Mayr (1942). The biological species concept emphasizes that reproductive isolation is the key characteristic between independent species (Zachos 2016;Nosil et al. 2017;Cupello & Vaz-de-Mello 2018;Huang 2020). Each species defined herein shows a unique morphology of the endophallite copulatrix. Therefore, sexual isolation between species of the P. endymion species group is expected, since differences in the morphology of the endophallites in Scarabaeinae dung beetles are considered as prezygotic mechanical barriers that may prevent interbreeding (Price 2005;Werner & Simmons 2008;Moretto & Génier 2020). The morphology of the endophallites has exhibited high levels of interspecific variation in other groups of Scarabaeinae dung beetles (Howden & Gill 1993;Joaqui et al. 2019;Moretto & Génier 2020), while this variation is expected to have a strong phylogenetic signal to discriminate different evolutionary lineages (Tarasov & Solodovnikov 2011;Tarasov & Génier 2015).