Helictopleurus halffteri Balthasar 1964: 623 (Figs 2b, 3d); Montreuil 2005b: 346;

a

b

c

d

e

f

Figure 2.

Type specimens of Helictopleurus.

a: Dorsal habitus and labels of the holotype of H. dorbignyi;  
b: Dorsal and frontolateral habitus and labels of the holotype of H. halffteri;  
c: Dorsal habitus and labels of the holotype of H. hypocrita;  
d: Dorsal habitus and labels of the paratype of H. perpunctatus;  
e: Dorsal and frontolateral habitus and labels of the syntype of H. clouei;  
f: Dorsal and frontolateral habitus and labels of the syntype of H. gibbicollis.  

a

b

c

d

Figure 3.

Distribution maps of Helictopleurus.

a: H. rudicollis (blue circles; black arrows indicate the type locality) and H. splendidus (red circles; red arrows indicate the type localities);  
b: H. clouei (red arrow indicates the type locality of H. gibbicollis syn. nov.);  
c: H. vadoni (red arrow indicates the type locality);  
d: H. halffteri (red arrow indicates the type locality of H. halffteri and H. dorbignyi). Question mark indicates the collecting localities of some of the type specimens of H. dorbignyi syn. nov. (=H. halffteri). These specimens may belong to an undescribed species.  

Helictopleurus dorbignyi Montreuil 2005a: 123 (syn. nov.) (Figs 2a, 3d);

Within the semivirens group, H. halffteri may be related to H. seminiger. Males can be distinguished by the clypeal tubercle simple (laterally connected to two ridges in H. seminiger) and the frontoclypeal carina trituberculate (simple in H. seminiger). No female specimens of H. seminiger are known, as the type series includes the male lectotype only (see "Taxon discussion" below).

Antsianaka and Lac Alaotra (Fig. 3d).

The Helictopleurus semivirens species-group includes 10 species: H. aeneoniger Lebis, 1960, H. cambeforti Montreuil, 2005, H. halffteri Balthasar, 1964, H. heidiae Montreuil, 2007, H. niger d’Orbigny, 1915, H. pseudoniger Montreuil, 2005, H. seminiger d’Orbigny, 1915, H. semivirens d’Orbigny, 1915, H. steineri Paulian & Cambefort, 1991 and H. tamatavensis Montreuil, 2005 (Montreuil 2005a).

Helictopleurus halffteri shares exclusive phenotypic traits with the members of the group, such as head ogival-shaped and elongated (unique within Helictopleurus); head of male often with clypeal tubercles, frontoclypeal carina and frontal tubercles and/or curved carina; dorsal side of the body very polished, fairly dark, dull to feebly shining; elytra visibly longer than pronotum with respect to the majority of Helictopleurus species.

Balthasar (1964) described H. halffteri on a single female specimen collected by the Perrot brothers in 1893 in Antsianaka and, after its description, the species name appeared only in one checklist (Montreuil 2005a). On studying the Helictopleurus of the semivirens group, Montreuil (2005a) discovered that the type series of H. seminiger, which allegedly consisted of one male and one female specimen, included instead two distinct species. Actually, the specimen that d’Orbigny (1915) identified as female turned out to be a male and was designated by Montreuil (2005a) as the holotype of the new H. dorbignyi. Therefore, the type series of H. seminiger currently consists of a unique male designated as the lectotype (Montreuil 2005a).

The type series of H. dorbignyi is composed of the male holotype collected in Antsianaka, lake Alaotra and multiple male and female paratypes collected further south, in the Ranomafana National Park and nearby localities (Fianarantsoa) (Fig. 3d). On studying the external morphology and genitalia of the type specimens of H. dorbignyi deposited in the MNHN, we realised that the type series is composed of at least two distinct species: one represented by the male holotype alone; the other represented by several males and females collected in Ranomafana. Therefore, in the light of the abovementioned facts and after examination of the holotype of H. halffteri, we conclude that:

(i) the morphology of the female holotype of H. halffteri and its type locality suggest that this specimen is conspecific with the male holotype of H. dorbignyi. Thus, H. dorbignyi is established as junior subjective synonym of H. halffteri (H. dorbignyi syn. nov.).

(ii) The study of the female genitalia of H. halffteri and female paratypes of H. dorbignyi collected in Ranomafana indicates that they belong to different species. Therefore, a new Helictopleurus species from Ranomafana is waiting formal description.

Interestingly, the unique type specimen of H. seminiger was collected from Antsianaka – which is the same type locality as H. halffteri – and the species has never been recollected since 1892. These circumstances would make the identity of this taxon questionable. However, during our visit to the Paris museum, we could not study the genitalia of the lectotype of H. seminiger. Possibly, the differences observed on the cephalic processes between H. seminiger and H. halffteri represent a simple variation of a same species. An extensive review of the semivirens group would help to sort out unresolved questions that still hamper the correct identification of these cryptic taxa.

Oniticellus rudicollis Fairmaire 1898: 399

Liatongus rudicollis: Fairmaire 1901: 134 (new combination);

Helictopleurus rudicollis: d’Orbigny 1915: 418 (new combination); Gillet and Boucomont 1927: 111; Balthasar 1941: 89; Lebis 1960: 72; Paulian 1986: 106; Montreuil 2005a: 133;

Helictopleurus hypocrita Balthasar 1941: 134 (syn. nov.) (Fig. 2c) ; Montreuil 2005a: 133; Bezdĕk and Hájek 2012: 321;

Helictopleurus rudicollis belongs to the rudicollis group and can be readily distinguished from other members of the group, H. rubricollis and H. cribricollis, by the pronotum and elytra metallic-green and shiny and elytra with lighter spots (elytra dark, dull, not metallic and without spots in both H. rubricollis and H. cribricollis). The separation of H. rudicollis from H. splendidus is still unclear, as the male of the latter was never described. Nonetheless, the following female characters could help in separating the two species: punctation of posterior third of pronotum evenly distributed in H. rudicollis (sparser in H. splendidus); lateral pronotal angles more expanded laterally in H. splendidus; median tubercle of frontal carina simple in H. rudicollis (bilobate in H. splendidus).

This species is widely distributed across eastern Madagascar, from the Sambava to Ifanadiana District (Fig. 3a).

Balthasar (1941) described H. hypocrita on a unique specimen, but no exact collecting locality was given. Without checking the holotype, Lebis (1960) assigned this species to the giganteus group, suggesting that the original description could refer either to H. undatus (Olivier, 1789) or H. rudicollis. Ever since, H. hypocrita appeared only in one checklist (Montreuil 2005a). In this study, we investigated and compared the external and genital morphology of the holotype of H. hypocrita with the type specimens of the members of the rudicollis group and we eventually concluded that H. hypocrita is a junior subjective synonym of H. rudicollis (H. hypocrita syn. nov.).

The Helictopleurus rudicollis group includes four species (Lebis 1960, Montreuil 2005b): H. rudicollis, H. cribricollis Lebis, 1960, H. rubricollis Lebis, 1960 and H. splendidus d’Orbigny, 1915. However, after examination of the syntypes of H. furcicornis Lebis, 1960, we deem that this species too could be considered an additional member of the same group. Helictopleurus furcicornis shares several characters with H. rudicollis: body metallic-green; elytra with a series of orange-brownish spots; long yellow setae along the lateral edges of the pronotum; tip of the parameres strongly curved downwards. However, the two species differ in the shape of the male frontal horn (conical in H. rudicollis; wider, with parallel sides and distally emarginated in H. furcicornis), pronotal punctuation (denser in H. rudicollis) and lighter spots on elytra (single transversal row in H. rudicoliis; elytral interval 4 with two additional spots, one in proximity of the base, one close to the apex).

Helictopleurus rudicollis was described from Tamatave and Antsianaka, which correspond to today’s Toamasina and Lac Alaotra, respectively, both located in central-eastern Madagascar (Viette 1991). Instead, the type series of H. splendidus includes specimens from Bémarivo (probably referring to a locality along the Bemarivo River, north-eastern Madagascar), Fianarantsoa and Fort Dauphin (central-eastern and south-eastern Madagascar, respectively) (d’Orbigny 1915) (Fig. 3a). Despite the multiple dung beetle surveys carried out over the last 20 years in the type and nearby localities, no additional specimens of H. splendidus have been captured or identified. On the other hand though, H. rudicollis is considered one of the most abundant species in these localities (Rahagalala et al. 2009). Therefore, given that the two species are morphologically very similar, the above statements raise a series of questions that need further investigation: (i) Have all the "H. rudicollis" specimens collected so far been identified correctly? (ii) is H. splendidus a valid species? (iii) If so, maybe this latter species has become extinct?

During a recent collecting expedition in Madagascar (February 2022), we collected a series of conspecific specimens in Mandraka Park (-18.914266, 47.92477098), Analamazoatra (-18.939524, 48.418760) and Mantadia (-18.84549399, 48.42834902) National Parks, including one male, that may belong to H. splendidus. However, a detailed comparison of the morphology of these specimens with the types of H. splendidus and H. rudicollis is needed to confirm this identification and the taxonomic status of H. splendidus.

Helictopleurus vadoni Lebis 1960: 99; Paulian 1986: 107; Montreuil 2005a: 134;

Helictopleurus parvulus Frey 1975: 305; Paulian 1986: 107 (synonymy);

Helictopleurus perpunctatus Balthasar 1963: 292 (syn. nov.) (Fig. 2d); Montreuil 2005b: 376;

Helictopleurus vadoni is readily distinguished from congeneric species by the following combination of characters: elytra dark, with metallic tinges and characteristic brownish-orange spots mostly concentrated on the basal half of the intervals 1–5; elytral intervals with erected setae; pronotum metallic-green, shiny, densely and evenly punctated and setose, discal punctures coarser.

This species occurs in the Sambava and Maroantsetra Districts, north-eastern Madagascar (Fig. 3c).

Helictopleurus perpunctatus was described on two female specimens, without exact collecting locality. According to Balthasar (1963), the holotype is in J. Schulze’s collection (probably in the Museum für Naturkunde, Berlin), but we could not examine it. In this study, instead, we investigated the morphology of the paratype (NMPC), which clearly indicates that H. perpunctatus is a female of H. vadoni. Given the original description and Balthasar's expertise on scarabs, we believe that both the holotype and paratype are conspecific. Therefore, H. perpunctatus is established as the junior subjective synonym of H. vadoni (H. perpunctatus syn. nov.).

Balthasar (1963) states that his conclusions on H. perpunctatus was drawn after consultation of the keys from d’Orbigny (1915). Therefore, it is likely that he overlooked the Helictopleurus that meanwhile were described by Lebis (1960). In so doing, Balthasar considers H. perpunctatus a close relative of H. infimus (Fairmaire, 1901) and provides a list of characters to separate the two species.

Lebis (1960) included H. vadoni in the fungicola-viridiflavus group, along with seven additional species. These Helictopleurus were subsequently separated into two groups: fungicola and viridiflavus (Montreuil 2005a). Today, the viridiflavus group comprises the following species (Montreuil 2005b): H. viridiflavus (Fairmaire, 1898), H. vadoni, H. infimus (Fairmaire, 1901), H. carbonarius Lebis, 1960, H. minutus Paulian & Cambefort, 1984, H. villiersi Paulian & Cambefort, 1984 and H. ambiguus Paulian & Cambefort, 1991. The majority of these Helictopleurus seems to be strictly associated with dry and semi-arid regions of western Madagascar. The dung beetle fauna of these areas has been poorly investigated and many of these Helictopleurus are only known from the type series, which often consist of single specimens.

Helictopleurus vadoni and H. viridiflavus are the only members of the group that occur in the humid-most eastern Madagascar, with occasional incursions into drier regions (Fig. 3c). Helictopleurus viridiflavus is a very distinct species, with elytra brownish and without spots; pronotum metallic-green to coppery, with elongate and very dense punctures.

Oniticellus clouei Harold 1869: 68; Harold 1880: 155; Fairmaire 1895: 13; Fairmaire 1898: 471;

Helictopleurus clouei: d’Orbigny 1915: 428 (new combination) (Figs 2e, 3b); Lebis 1960: 111; Gillet and Boucomont 1927: 110; Paulian 1986: 104; Montreuil 2005a: 134;

Oniticellus gibbicollis Fairmaire 1895: 16;

Helictopleurus gibbicollis d’Orbigny 1915: 433 (new combination) (syn. nov.) (Figs 2f, 3b); Gillet and Boucomont 1927: 110; Lebis 1960: 119; Paulian 1986: 105; Montreuil 2005a: 134;

Helictopleurus clouei is distinguished from other members of the H. quadripunctatus group by the pronotum metallic-green and shining (opaque, dark green to bluish in the other species); elytra orange to dark brown (black with a medial yellow stripe in H. perrieri), with poorly-defined dark spots at the base and apex (spots more distinct in H. quadripunctatus). Harold (1869) suggests that H. clouei may be related to H. quadripunctatus, but specimens of H. clouei are visibly smaller.

This species occurs in northern Madagascar and is relatively common in open habitat (Fig. 3b).

According to Harold (1869), the original description of H. clouei was allegedly based on a single female specimen without exact type locality. In the present study, the examination of this unique syntype allowed us to confirm that it is actually a male. This species is today assigned to the quadripunctatus group, together with H. quadripunctatus (Olivier, 1789), H. perrieri (Fairmaire, 1898) and H. gibbicollis (Fairmaire, 1895) (Lebis 1960, Montreuil 2005a).

Amongst the numerous Helictopleurus authored by L. M. H. Fairmaire (1820–1906), in 1895, he described H. gibbicollis from a single male specimen collected by C. A. Alluaud (1861–1949) in Diego Suarez (Fairmaire 1895). This species was originally assigned to the semivirens group (Lebis 1960) and later moved to the quadripunctatus group (Montreuil 2005a). Despite Fairmaire’s explicit statement about the collecting event, it is still unclear why Lebis (1960) and Paulian (1986) indicate "Mandritsara" as type locality of the species.

Over the years and despite the intense dung beetle surveys carried out in Diego Suarez and surroundings (e.g. Hanski et al. (2007)), H. gibbicollis has never been recollected nor mentioned in any work. This makes the taxonomic identity of this species fairly questionable and in urgent need of validation.

The morphological examination of the syntypes of H. clouei and H. gibbicollis allowed us to establish the latter as a junior subjective synonym of H. clouei (H. gibbicollis syn. nov.). Probably, the different colour of the elytra of the two specimens (dark brown in the syntype of H. gibbicollis and bright orange in H. clouei) might have confused former authors, who kept considering H. clouei and H. gibbicollis as distinct species. However, the shape of the cephalic ornaments (carinas and frontal horn) and pronotum, the pronotal tegument, the colour pattern of elytra and the shape of the parameres clearly indicate that the two specimens are conspecific.

This new synonymy reduces the number of species of the quadripunctatus group to three.