Frolov, A.V. 2012. Diagnosis, classification, and phylogenetic relationships of the orphnine scarab beetles (Coleoptera, Scarabaeidae: Orphninae). Entomological Review, 92, 782-797.

Original Russian text: Фролов, А. В. 2012. Диагноз, классификация и филогенетические отношения пластинчатоусых жуков-орфнин (Coleoptera, Scarabaeidae, Orphninae). Энтомологическое обозрение, 91(2): 332-351.

DOI: 10.1134/S0013873812070056

Diagnosis, classification, and phylogenetic relationships of the orphnine scarab beetles (Coleoptera, Scarabaeidae, Orphninae)

A.V. Frolov

Zoological Institute, Russian Academy of Sciences, St. Petersburg, 199034 Russia Received February 20, 2012

Abstract

Orphnine scarab beetles (Orphninae) are widely distributed in tropical and subtropical regions of southern continents except for Australia. Catalogue of nominal taxa of orphnines includes 2 tribes, 15 genera, and 193 species. Diagnosis of the group, based on adult morphological characters, is as follows: antennae 10-segmented with 3-segmented club; mandibles with 2-4 scissorial teeth and well developed mola; labrum and mandibles protruding past clypeus and can be seen from above; scutellum well developed in winged species, reduced but distinct in wingless species; wings with distinct anal area; apices of anterior tibia in males without spur but normally with a few robust setae; anterior coxa with longitudinal hollow on anterior surface; tarsi with 2 similar claws; middle and hind tibiae with 2 apical spurs; 2 abdominal sternite with sub-triangular to rounded plectrum; dorsal surface of hind coxae with oval flat stridulatory file; pygidium partly hidden under elytra; parameres symmetrical; bursa copulatrix sacciform, membranous; spermatheca C-shaped, not sclerotized; accessory vaginal glands developed; abdomen with 2 sclerotized tergites (VII-VIII) and 6 visible sternites (III-VIII). Preliminary phylogenetic analysis based on 47 characters of adult morphology shows that the tribe Aegidiini Paulian is a natural, monophyletic group. The genus Stenosternus Karsch, described from single specimen from São Tomé Island (Gulf of Guinea) is morphologically more similar to New World taxa than to Old World ones and is provisionally placed in Aegidiini. The tribe Orphnini Erichson seems non-monophyletic and has no synapomorphies. The genus Orphnus is apparently a polyphyletic group and it needs taxonomic revision. Hypothesis about sister-group relationship of Orphninae and Allidiostomatinae, based on molecular data, is not supported by morphological characters. Stridulatory organs (the putative synapomorphy of Orphninae + Allidiostomatinae) are not identical in these groups; mouthparts and female genitalia are essentially different. Orphninae have chewing mouthparts with large scissorial teeth and well developed mola, which is characteristic for generalist saprophagous species. Allidiostomatinae have mandibles with scissorial teeth and mola reduced; they also have sclerotized bursa copulatrix and sclerotized mandibular duct which opens on ventral side near condyle. Considering the present day development of alpha-taxonomy of most orphnine taxa, especially the speciose genus Orphnus, it seems premature to propose changes in higher classification of the subfamily. To clarify the phylogenetic position of the Orphninae among scarab beetles it is essential to include representative members of all taxa of orphnine lineage (sensu Browne, Scholtz, 1998) into analysis.

Introduction

Orphnines (Orphninae) are one of the little known subfamilies of scarab beetles. They are rare in collections but rather widely distributed in tropical and subtropical regions of southern continents except for Australia. The name of the group was proposed (as Orphnidae) by Erichson (1847). Contemporary superspecific classification of orphnines is mostly based on the works of Renaud Paulian. He revised the genus Orphnus and divided it into 6 subgenera (Paulian, 1948), and later (Paulian, 1984) established 2 tribes, Aegidiini and Orphnini (subfamilies Aegidiinae and Orphninae in the original work, since Paulian, in his later publications, treated orphnines as a family). Past researches gave higher priority to characters of sexual dimorphism, especially to processes on the head and pronotum in males. These characters vary significantly in the members of the subfamily and, generally, have low phylogenetic value in scarab beetles. In the present work, I compare the contemporary classification of orphnines with the results of phylogenetic analysis based on a larger set of characters. The clarified diagnosis of Orphninae is also presented.

Large material used in this work is deposited in or borrowed from the following organizations: Museum für Naturkunde, Humboldt-Universität (Berlin), Zoological Institute RAS (ZIN, St.-Petersburg), Institut royal des Sciences naturelles de Belgique (Brussels), natural history museums in Geneva, London, Paris and Stockholm, Oxford University Museum of Natural History (Oxford), Koninklijk Museum voor Midden-Afrika (Tervuren), Národní muzeum (Prague), and Transvaal Museum (Pretoria).

Preparation of genitalia follows the common technique used in entomological research. Standard methods of dissecting and scanning electron microscopy were used for morphology examination and preparation of illustrations. Phylogenetic analysis methodology is described below in the corresponding section.

The most comprehensive published catalogue of the world orphnines (Arrow, 1912) does not provide insight into taxonomy of the group since it is largely outdated, lacking more than a half of the described species, and includes a few genera which are no longer considered the members of the subfamily. Therefore, an updated catalogue of the generic and specific names of the orphnines described to date is provided.

Main results of the present work were reported on the Zoological Sessions of ZIN (Frolov, 2009).

Taxonomic composition and distribution of orphnines

Different authors established more than 15 genera of orphnines including a few monotypical ones and 2 relatively speciose, Orphnus Macley and Hybalus Brullé.

Orphnines are widely distributed in tropical and subtropical regions of southern hemisphere. Six regional faunas can be distinguished with the largest one being the fauna of the Afrotropical biogeographic region. Afrotropical fauna includes the majority of the species of the genus Orphnus and 3 monotypical genera – Craniorphnus Kolbe, Goniorphnus Arrow, and Hybaloides Quedenfeldt. Orphnines occur throughout the Afrotropical region except for southern Arab Peninsula (where they will probably be found), and south-western part of Southern Africa (arid region of Namaqualand and Namib Desert).

Indo-Malayan fauna is rather poor and not very distinctive. Six species of the genus Orphnus are known from the Hindustan, Sri Lanka Island, and Indo-China. These species are very similar to some African members of Orphnus, and probably their ancestor or ancestors migrated from Africa into Southern Asia not until Miocene.

Mediterranean fauna comprises Hybalus and Chaetonyx Schaum with all species being wingless and having reduced eyes. This fauna is distributed up to Iberian and Balkan peninsulas in the north, but is the most diverse in the Northern Africa.

Madagascan fauna comprises 4 genera (Pseudorphnus Benderitter, Madecorphnus Paulian, Triodontus Westwood, and Renorphnus Frolov et Montreuil) and 30 species, some of which were described recently (Frolov, 2010; Frolov, Montreuil, 2009). Orphnines are distributed throughout Madagascar except for hyper-arid south-western region; they are not known from Comoro and Mascarene islands.

New World fauna comprises 4 genera (Aegidium Westwood, Aegidiellus Paulian, Aegidinus Arrow, and Paraegidium Vulcano et. al.,) and 24 species distributed in Caribbean, Guiana, and Amazon biogeographic regions (Paulian 1984, Colby 2009).

Small but distinctive orphnine fauna of São Tomé Island (Gulf of Guinea) comprises a single species of the monotypic genus Stenosternus Karsch. Although the island is relatively close to Africa mainland, S. costatus Karsch is morphologically more similar to members of New World taxa than to African ones. Zoogeographic affinities of the faunas of São Tomé and Brazil were mentioned in the literature and in the case of a few longhorn beetle species is was shown that they had been inadvertently imported from Brazil in colonial times. However import of S. costatus seems improbable and the available data suggest that it is indigenous to São Tomé. Discussing this question in more detail is however beyond the scope of this paper.

All regional faunas, except for Indo-Malayan, are highly distinctive and do not share genera or species. Orphnines are absent from Notogea (Australasia), Patagonian Province of Neotropical Realm, Holarctic Realm (except for southern Mediterranean and transitional zone of Sino-Tibetan Mountains), as well as insular part of Indo-Malayan Province.

Morphological characters of orphnines

The comprehensive description of the orphnine morphology is beyond the scope of the present work. Below are discussed the characters that potentially have phylogenetic value and clarify the diagnosis of the group.

Mouthparts and alimentary channel

Orphnines have mouthparts of chewing type. Mandibles are mostly symmetrical, about the same length, normally with 2–4 well developed teeth (Fig. 1. 1). Exception to this are the males of the Madagascan genus Madecorphnus Paulian, which may have highly asymmetrical mandibles with the right one being up to 2 times, or more, longer than the left (Paulian, 1992, Frolov, 2010). Maxillae have separate lacinia and galea which normally bear thick spinules along with thin setae (Fig. 1. 2). In general, this type of mouthparts is characteristic of generalist saprophages and, probably, is similar to the ancestral type of scarab beetle mouthparts.

Fig. 1. Orphnus spp. and Allidiostoma spp.

Fig. 1. Orphnus spp. and Allidiostoma spp. 1, 2 – O. ellenbergeri; 3, 4 – A. ramosae; 5 – A. strobeli; 6 – O. macleayi. 1, 4 – left mandible; 2, 3 – maxilla (3 – maxillary palpus is broken); 5, 6 – fore coxa and femur; or. md – opening of mandibular duct, con – condyle; pr. fm – fore femur, pr. cx – fore coxa, pr. cx. fv – hollow of fore coxa.

There are no direct data about orphnine feeding behavior. Some assumptions can be inferred from the information gathered from collectors and from the labels of the collection specimens. In Madagascar, orphnines, notably Pseudorphnus hiboni Paulian, were collected by litter sifting and in the pitfall traps baited with fish and chicken intestine (Frolov, Montreuil, 2006). In the case of pitfalls, it is uncertain whether the beetles were attracted to the baits or captured occasionally. Short-time exposures of the traps might suggest that the beetles were attracted to the carrion. However the collectors did not set unbaited traps or sift litter in the same biotopes. It is possible that the population density was high enough for accidental trapping in pitfalls. Adults of the South American genus Aegidium Westwood were collected from under rotten banana stems. Orphnines have not been collected from dung, carcasses, or from other specific substrates. Hind gut of almost all specimens that I examined contained well visible food particles (Fig. 3, 1).

The mouthparts of the members of the putatively related subfamily Allidiostomatinae (Fig. 1, 3, 4) differ significantly from those of the orphnines (Fig. 1, 1, 2). Arrow (1904) drawn attention to their reduction. However not all mouthparts are reduced but only mandibles, especially their molar parts and scissorial teeth. The mandibles are of normal length in comparison to the body length of the beetles and strongly sclerotized (Fig. 1, 4). Such mandibles are obviously unsuitable for feeding on semisolid (like orphnines) or liquid (like filtering coprophages of the subfamily Scarabaeinae) substrates. It is possible that adult allidiostomatines do not feed or feed on sap or flower nectar, however no data are available as for this. No specimens I examined had any visible content in the hind gut (Fig. 3, 2). Although hind gut of allidiostomatines cannot be considered vestigial, its relative size is much smaller in comparison to that of orphnines (Fig. 3, 1).

Examination of the mandibles of A. ramosae Martinez revealed an interesting undescribed structure. This species has mandibles with short sclerotized duct which opens on the ventral side near condyle. The duct penetrates the mandibular cavity and slightly protruding past mandibular base (Fig. 1, 4). The function of this structure is unclear. It can be supposed that the duct serves for excretion of some gland products. The glands were not found but being of endodermal origin they most probably are not preserved in the dry collection specimens. It is possible that such structure is present in other Allidiostoma species or represents an autopomorphy of the Allidiostomatinae. However, material suitable for histological research is needed to clarify the function of this mandibular duct.

Fore legs

The absence of the apical spur on the fore tibiae in male orphnines is characteristic for the subfamily. In general, absence or modifications of fore tibia spurs occur in many scarab groups and probably developed many times and independently. Fore tibia spur can be absent in one or both sexes, in some species of a genus, or in all species of some genera and higher taxa, for example in chafers of the subfamilies Melolonthinae and Rutelinae. However, there are no subfamilies but Orphninae where the spur is absent in all member and where this absence is probably inherited from the common ancestor of the group. It is also characteristic for male orphnines that they have a few apical setae on fore tibia (in the place of the absent spur) that are thicker than the others. In most cases there are 3–5 such setae which differs clearly from other, slender setae.

The presence of a longitudinal hollow on anterior surface of fore coxa (Fig. 1. 6) is another character of the orphnines. This hollow is well developed in both sexes of all orphnine genera except for Hybalus Brullé, which probably represent a secondary lost. In Aegidinus Arrow, the hollow is interrupted medially (Colby, 2009). The function of this hollow is unclear. The hollow is concealed in the coxal cavities while a beetle is walking; it opens only when the fore legs are appressed to the pronotum.

Stridulatory apparatus

One of the characteristic features of the orphnines is the specific stridulatory apparatus. This orphnine type of stridulatory apparatus is present in all species of the group.

Stridulation in scarab beetles is long known and rather well studied thanks to Arrow (1904), who described stridulatory apparatus of members of more than 60 genera of Scarabaeoidea. This work is up to date the most comprehensive synopsis of stridulation in scarab beetles. The common stridulatory apparatus of beetles consists of two parts, the plectrum – singular structure with scraper function, and a group of more or less uniform and ordered structures – the stridulatory keels, which together resemble a washboard. In English language literature, for the latter the terms “stridulatory file” and “stridulatory comb” are used. I am following Arrow in calling it “stridulatory field”. Stridulatory apparatus is always doubled, symmetrically situated on both sides of a beetle. Stridulation in most of the described cases is resulted from vibration of the abdomen which bears a pair of plectra. Stridulation fields can be situated on different parts of the body adjacent to the abdomen, usually on the hind coxa or apices of elytra.

Fig. 2. Aegidium columbianum, Allidiostoma spp. and Orphnus spp.

Fig. 2. Aegidium columbianum, Allidiostoma spp. and Orphnus spp. 1, 3 – Ae. columbianum; 2, 4 – A. ramosae; 5 – O. macleayi; 6 – A. strobeli. 1, 2 – abdomen in ventral view with plectrum; 3, 4 – hind coxa in dorsal view; 5, 6 – stridulatory file, scanning electron micrograph; pl – plectrum, pars. str – stridulatory field.

Stridulatory apparatus is present in all nominal genera of Orphninae and in all species which I studied (more than 80 % of Orphninae species). The apparatus is rather uniform in all members of the group. Stridulatory field is situated basally on the dorsal surface of hind coxa (Fig. 2, 3, 5). Shape of the field varies from relatively small elongated ellipsis to wide, occupying reasonable part of the coxa surface. Plectrum is triangular to trapezoidal, with the apex somewhat rounded, highly sclerotized and somewhat turned up (Fig. 2, 1). This turned up apex is a scraper which scratches the stridulatory field. This type of stridulatory apparatus is only known in the orphnines and is a putative autopomorphy of the group.

Allidiostomatinae type of stridulatory apparatus is similar to the orphnine type in respect of its position, however it differs in its structure. In Allidiostomatinae, the stridulatory field consists of shorter, finer, and more numerous stridulatory keels situated across a transversal, feebly elevated band on the coxal surface (Fig. 2, 4, 6). The plectrum is formed by a thickening on the 2nd abdominal sternite margin (Fig. 2, 2). Thus, as opposite to orphnines, allidiostomatines have wide plectra and narrow stridulatory fields. The shape of the allidiostomatine stridulatory field is similar to that of the members of the Geotrupidae. However in geotrupids, it is situated medially and the plectrum is formed by the 3rd abdominal sternite.

Fig. 3. Aegidium columbianum and Allidiostoma ramosae.

Fig. 3. Aegidium columbianum and Allidiostoma ramosae.

1, 3, 5 – Ae. columbianum; 2, 4 - A. ramosae. 1, 2 – female genitalia and hind gut; 3, 4 - – female genitalia in ventral view; mesosternum and metasternum in lateral view; bur. cop – bursa copulatrix, gl. acc – vaginal gland, gl. rec – spermatheca gland, mesost – mesosternum, metast – metasternum, or. cox – hole connecting middle coxal cavities, ovd – oviduct, parapr – paraproct, pal. vag – vaginal palpus, proct – groctiger, rec. sem – spermatheca, rect – hind gut.

Characters and their codes used in the phylogenetic analysis

1. Ventral side of mandibles: without keels – 0; with a keel – 1.
2. Number of scissorial mandibular teeth: 2 – 0; 3 – 1; 4 – 2; 1 – 3.
3. Outer margin o mandibles: not serrate – 0; serrate – 1.
4. Shape of outer margin o mandibles: rounded – 0; angulate – 1.
5. Left and right mandibles: symmetrical or subsymmetrical – 0; asymmetrical – 1.
6. Apex of mandible: not widened – 0; widened – 1.
7. Mola: well developed – 0; reduced – 1.
8. Molar area of left mandible: solid, smooth – 0; with deep regular relief – 1.
9. Right mandible in males: approximately as long as left – 0; can be much longer than left – 1.
10. Lacinia: with strongly sclerotized apex an 1 spinule – 0; with spinule-shaped apex and 4 spinules – 1; with elongated apex and without spinules – 2; with bifurcate or trifurcate apex – 3; with bifurcate apex and a spinule – 4; with short apex and thin setae – 5.
11. Galea: with spinule-shaped apex, adjacent spinule and bunch of long setae – 0; without distinct apex, with butch of setae some of which are robuster than others – 1; with digitiform apex and 1 or 2 spinules – 2; with poorly pronounced apex and 2 spinules – 3; with poorly pronounced apex and butch of setae – 4; with long digitiform apex and a few falcate setae – 5; with butch of setae (no distinct apex) – 6.
12. Second segment of labial palpi: without triangular process – 0; with triangular process – 1.
13. First (basal) segment of antennal club: perpendicular to 7th antennal segment – 0; inclined to 7th antennal segment – 1.
14. First segment of antennal club: encloses other segments of antennal club – 0; does not enclose other segments – 1.
15. First segment of antennal club: glabrous – 0; with sparse setae, mostly apically – 1; with dense pubescense – 2; with a few setae, mostly medially – 3.
16. Fore margin of labrum: more or less bilobate – 0; convex medially – 1; almost straight or feebly convex – 2; trapezoidal, serrate – 3.
17. Fore margin of labrum: pubescent – 0; not pubescent, heavily sclerotized – 1.
18. Shape of basal sclerotized structure of labrum: oval to rounded triangular – 0; cordate – 1; wide, oval to rounded triangular – 2; triangular with feebly concave anterior margin – 3.
19. Apical sclerotized structure of labrum: more or less distinct – 0; absent – 1; in shape of 2 short processes – 2.
20. Longitudinal medial band in basal sclerotized structure of labrum: more or less distinct, reaching base of structure – 0; indistinct – 1.
21. Apical sclerotized structure of labrum: considerably smaller than basal structure, not reaching fore margin of labrum – 0; almost as large as basal structure, reaching fore margin of labrum.
22. Elytral striae: as pale fine lines – 0; indistinct – 1; in shape of row of semicircular punctures – 2.
23. Elytral surface: with relatively large rounded punctures, colored as the rest of elytral surface – 0; with minute punctures – 1; with elongated punctures, paler than the rest of elytral surface – 2; with semicircular punctures – 3; with U-shaped punctures, directed posteriorly – 4; with U-shaped punctures, directed anteriorly – 5.
24. Humeral umbones: distinct – 0; absent – 1.
25. Elytra: not fused – 0; fused along suture – 1.
26. Elytral disc basally: not bordered – 0; bordered – 1.
27. Base of elytra adjacent to pronotum: more or less convex – 0; more or less concave – 1.
28. Sides of elytra: glabrous – 0; pubescent with short dense setae – 1; pubescent with long sparse setae – 2; elytra entirely pubescent with long dense setae – 3.
29. Elytral surface: smooth – 0; granulate – 1.
30. Apical spur of fore tibia: present in both sexes – 0; absent in males – 1.
31. Apex of fore tibia: with process, parallel to inner margin of tibia, – 0; without process – 1.
32. Apical outer tooth of fore tibia: directed at right or obtuse angle to inner margin of tibia – 0; directed in parallel with inner margin of tibia – 1.
33. Apical setae of fore tibia in male: thin, similar to setae on inner margin of tibia – 0; thickened (usually 3 setae located on the place of absent spur) – 1; absent – 2.
34. Hollow on fore coxae: absent (Fig. 1, 5) – 0; present (Fig. 1, 6) – 1.
35. Middle tibiae: without transverse keel – 0; with transverse keel – 1.
36. Hind tibiae: without transverse keel – 0; with transverse keel – 1.
37. Stridulatory field on hind coxae: absent – 0; present – 1.
38. Stridulatory field: oval, flat – 0; in shape of transversal, feebly elevated band on the coxal surface – 1.
39. Triangular or trapezoidal plectrum on 2nd abdominal sternite: absent – 0; present – 1.
40. Stridulatory keels: fine, relatively numerous, separated by more or less equal intervals – 0; less numerous, medial keels wider and separated by wider intervals than lateral keels – 1.
41. Apices of middle and hind tibiae: with fine setae near insertions of tarsus and spurs – 0; without such setae – 1.
42. Insertion of tarsus on hind tibia apex: located near dorsal margin – 0; located in medially or closer to ventral margin – 1.
43. Distance between apical spur insertions in middle and hind tibiae: approximately the same – 0; considerably smaller in middle tibia where the spurs are almost adjacent – 1.
44. Metepisternum: more or less triangular – 0; more or less trapezoidal, widened posteriorly to form an additional “lock” for closed elytra – 1.
45. Middle coxal cavities: separated – 0; connected by a hole (Fig. 3, 5), – 1.
46. Mandibles: without sclerotized channel – 0; with short sclerotized duct which opens on the dorsal side near condyle (Fig. 1, 4) – 1.
47. Bursa copulatrix: membranous, not sclerotized (Fig. 3, 3) – 0; digitiform, sclerotized – 1 (Fig. 3, 4).

Phylogeny and superspecific classification of orphnines

Computer-aided phylogenetic analysis was conducted for 29 terminal groups including members of all nominal genera and subgenera of orphnines, except for subgenus Cerhomalus. Members of two genera of Hybosoridae and one species of Allidiostoma were chosen as outgroups. Of the 47 characters described above 8 are parsimony uninformative as, in the present analysis, they are autopomorphies of outgroups and a few orphnine genera. The analysis was conducted using heuristic algorithm of NONA software (Goloboff, 1993), and yielded 20 most parsimonious trees (length 94, CI = 77, RI = 86). The trees have very similar topology and differs chiefly by the positions of Orphnus giganteus and O. strangulatus (Figs. 4 and 5).

It should be emphasized that the present analysis was not aimed at testing sister-group relationship of Orphninae and Allidiostomatinae, therefore the characters 14, 15, 17, 37, 41, and 42 (Figs. 4 and 5) should not be considered the synapomorphies of these groups. The opinion about sister-group relationship of Orphninae and Allidiostomatinae seems to be based mostly on the superficial similarity of adults rather than on synapomorphies. Both groups have similarly situated stridulatory apparatus which, however, differs in its structure and might not be homologous. Structure of mouthparts and female genitalia are essentially different in Orphninae and Allidiostomatinae. However, recent results of molecular systematic methods used to analyze 28S DNA fragments (Ocampo, Hawks, 2006; Ocampo et al., 2010), provide some evidence of possible close phylogenetic relationships of these two groups. On the cladograms, presented in these publications, Orphninae and Allidiostomatinae form one cluster. Bootstrap support for this cluster is poor in both cases, though.

On the cladograms presented here (Figs. 4 and 5), one can see that majority of branches are supported by non-homoplastic characters.

Fig. 4. One of 20 most parsimonious cladograms of the subfamily Orphninae

Fig. 4. One of 20 most parsimonious cladograms of the subfamily Orphninae, showing distribution of 47 morphological characters among 29 terminal taxa. Outgroups are italicized, Orphnus species are in bold. AFR – Afrotropical Region, MDG – Madagascar, MDT – Mediterranean, SCA – South and Central America, ST– São Tomé. See text for other explanations.

Fig. 5. One of 20 most parsimonious cladograms of the subfamily Orphninae

Fig. 5. One of 20 most parsimonious cladograms of the subfamily Orphninae, showing distribution of 47 morphological characters among 29 terminal taxa. Legend and abbreviation see in fig. 4.

A few branches remain unresolved but the results allow to draw some conclusions.

No one of the outgroups appears within Orphninae cluster. Monophyly of the orphnines is supported by 8 synapomorphies. Three of these synapomorphies pertain to the stridulatory apparatus and fore coxa; these characters are not known in other Scarabaeidae and can be considered autopomorphies of the orphnines (if the stridulatory apparatus of Orphninae and Allidiostomatinae is considered non-homologous).

Well isolated is the branch that includes 5 genera from the tropical New World and São Tomé Island (Figs. 4, and 5). This branch corresponds to the tribe Aegidiini Paulian, except for Stenosternus, which was unknown to Paulian. Adults of these taxa have metepisterna widened posteriorly (forming additional “lock” for closed elytra) and share a few other characters. For example, these genera, except for Stenosternus, have middle coxal cavities connected by a hole (Fig. 3, 5); this character is unknown in other scarab beetles. Although S. costatus is highly distinctive due to hind tarsi modified to spurs and elongated and depressed body combined with aptery, this species is rather similar to members of Aegidium. I provisionally place Stenosternus in the tribe Aegidiini based on the morphological similarity with New World taxa. S. costatus is so far know from the only male holotype and additional material is needed to clarify its taxonomic position.

Well isolated is also the group consisting of 2 Mediterranean genera, which probably originated from a common apterous ancestor. It can be noted that the cladograms suggest their closer relationship with South American taxa rather than Afrotropical or Indo-Malayan ones. They share a few characters of the mouthparts, especially the mandibles. However it is possible that the shared character states are homoplastic rather than homologous.
It can be concluded from the results of the phylogenetic analysis that the tribal classification of the orphnines needs revision. While the tribe Aegidiini is apparently a natural, monophyletic group, the Orphnini seems paraphyletic group having no synapomorphies. It is also probably that the genus Orphnus is a paraphyletic group and needs a revision.

The phylogenetic analysis presented here is preliminary and aimed at bringing the problem to light and planning the ways to solve it. Changes of the Orphninae classification and the position of the group on the evolution tree of Scarabaeidae appear necessary, but they require that at least representative members of all orphnine lineage taxa (sensu Browne, Scholtz, 1998) be included in the analysis. Considering the present-day state of the development of alpha-taxonomy of majority of orphnines, especially the genus Orphnus, it’s premature to alter the current classification. Results of Colby also agree with this conclusion, although her analysis includes fewer taxa and the branches are less resolved (Colby, 2009).

The clarified diagnosis of the Orphninae, based on adult morphological characters, is as follows: antennae 10-segmented with 3-segmented club; mandibles with 2-4 scissorial teeth and well developed mola; labrum and mandibles protruding past clypeus and can be seen from above; scutellum well developed in winged species, reduced but distinct in wingless species; wings with distinct anal area; apices of anterior tibia in males without spur but normally with a few robust setae; anterior coxa with longitudinal hollow on anterior surface; tarsi with 2 similar claws; middle and hind tibiae with 2 apical spurs; 2 abdominal sternite with sub-triangular to rounded plectrum; dorsal surface of hind coxae with flat stridulatory file basally; pygidium partly hidden under elytra; parameres symmetrical; bursa copulatrix sacciform, membranous; spermatheca C-shaped, not sclerotized; accessory vaginal glands developed; abdomen with 2 sclerotized tergites (VII-VIII) and 6 visible sternites (III-VIII).

Acknowledgments

I am thankful to all curators who provided material for this work. I am especially thankful to Olivier Montreuil (Muséum national d'Histoire naturelle, Paris), Marc De Meyer (Koninklijk Museum voor Midden-Afrika, Tervuren), Dirk Ahrens (Zoologische Forschungsmuseum Alexander Koenig, Bonn), Giulio Cuccodoro (Muséum d'histoire naturelle, Geneva), and Vladimir Gusarov (Naturhistorisk museum, Oslo), for their support over the past years.

This work was partly funded by Belgian Science Policy, National Museum of Natural History, Paris, Norwegian Research Foundation, Royal Society of UK, Russian Foundation for Basic Research (grant10-04-00539a), and Ministry of Education and Science of Russian Federation (contract 16.518.11.7070).

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