Hamonthophagus, Roggero & Dierkens & Barbero & Palestrini, 2017

Roggero, Angela, Dierkens, Michael, Barbero, Enrico & Palestrini, Claudia, 2017, Combined phylogenetic analysis of two new Afrotropical genera of Onthophagini (Coleoptera, Scarabaeidae), Zoological Journal of the Linnean Society 180, pp. 298-320 : 310-312

GENUS HAMONTHOPHAGUS GEN. NOV.

Type species: Onthophagus bituberculatus Olivier, 1789 .

Included species: At present five Afrotropical medium-sizes species ( Figs S2, S 3 – Appendix 4, frontal carina and simple vertex carina). The granulo-punctuate pronotum is not very convex, and has evident anterior angles with divergent apices that are inferiorly prolonged to a strong prosternal carina. Head and pronotum are usually black or dark brown. The elytra are flat, narrowed backwards, with marked striae and interstriae, extremely variable in coloration, ranging from evenly black to yellow with a discal dark spot.

Sexual dimorphism was shown in the protibia (carrying a tooth on the inner margin only in males) and pygidium (far more developed in males than females), as is common in Onthophagini .

Supporting Information) can be included in the genus Hamonthophagus gen. nov., namely: H. acutus ( d’Orbigny, 1908) , H. biturberculatus (Olivier, 1789) , H. depressus (Harold, 1871) , H. fallax ( d’Orbigny, 1913) and H. laceratus (Gerstaecker, 1871) .

Diagnosis: The species included in the genus Hamonthophagus are strictly allied, and share a combination of characters that distinguishes them from the other Onthophagini : the anterior margin of the clypeus mostly sinuate and bidentate, and both head carinae poorly developed (i.e. slightly marked Epipharynx: The epipharynx ( Fig. 2) is characterized by a rounded anterior margin gently notched in the middle, abundant and widespread acropariae, and well-developed corypha. The pubescence of the haptomerum is thick, the chaetopariae are almost rectilinear, constituted by short and dense setae. The anterior epitorma is longitudinal and narrow, the proplegmatium well sclerotized and arched, the apotormae are present, and the crepis is small, sharp and left-turned. The dexiotorma and laeotorma are slightly asymmetrical.

Male genitalia: The male is characterized by a medium-sized phallotheca (or aedaegus, Fig. 7) with symmetrical parameres, and well-developed apices, carrying ventrally a symmetrical expansion. The membranous internal sac (or endophallus, Fig. 8)

carries a hook-shaped and well-sclerotized primary sclerite, and some small accessory sclerites.

Female genitalia: In females, an asymmetrical, well-sclerotized funnel-shaped area is evident in the vagina ( Figs 9, 10), and is perhaps the most obvious character of the genus. The membranaceous and plurisinuate infundibulum is barely visible, being basally located at a very low position, just on the oviductus. The receptaculum seminis ( Figs 9, 10) is curved in the distal third, more enlarged at base and tapering to an apex, with a large desclerotized area medially.

Specific diagnosis: The Hamonthophagus species can be distinguished on the basis of some external features, such as the body pubescence, the elytral striae and the punctuation of pronotum and pygidium. Clear differences in shape were underlined by the geometric morphometrics analysis of head, pronotum, elytron and mentum (see above). Marked differences can also be highlighted by analysis of the epipharynx (always, according to the geometric morphometrics approach) and genitalia.

The pubescence covering the body consists of thick, ochreous and truncated setae that are short in H. depressus , H. acutus and H. fallax , and longer in H. bituberculatus , while in H. laceratus the setae are very elongate, thinner and not truncated.

The pronotum has a characteristic punctuation with varyingly sized, closely spaced, double points often carrying a hook-shaped granule never covering the point. While the points are usually dense (but excluding H. laceratus ), in H. bituberculatus only the larger points bear the minute and flat granules, while in H. acutus , H. fallax and H. depressus , the majority of the evident points carry well-developed and thick granules. Hamonthophagus laceratus is characterized instead by sparse and superficial points, with very minute and scattered granules.

The elytral striae are constituted by a very narrow line with larger points, except H. laceratus , where there are instead large striae with small points. Rasping, dense small setigerous points are present on the interstriae, and in H. acutus and H. bituberculatus the granules are small, while in H. depressus and H. fallax they are broader and evident. Again, in H. laceratus the points are rade, and almost inapparent, with few, very small granules. Hamonthophagus fallax usually carries an evident testaceous dot on the proximal sides of the elytra, and these dots are distally narrower than those in H. depressus .

In H. acutus , the pygidium is covered by superficial points and evident, roundish and small granules, while in H. depressus and H. fallax the dense, large setigerous points are without granules on the disc, sometimes carrying rough points only on the sides. Besides, the latter species both have an evident and cerebroid microsculpture on the surface, which in H. acutus is less marked. The pygidium of H. bituberculatus has an opaque, smooth surface with few, scattered, shallow points (sometimes with minute granules), but an evident, very thick microsculpture. Also in H. laceratus , the pygidium is almost smooth, with an evident microsculpture, with only few and sparse points lacking granules.

The fore margin of the epipharynx ( Fig. 2) is only weakly notched in the middle in H. acutus , while in H. bituberculatus , H. depressus and H. fallax the notch is V-shaped, more marked and large. In H. laceratus the fore margin is slightly more squared than in the other species. The apotormae are less developed in H. bituberculatus and H. laceratus than in the other species. The crepis is more reduced in H. acutus and H. fallax . The medial triangular sclerotized area of the proplegmatium is far shorter in H. fallax than in the other species. In H. laceratus , the rear sclerotized part between the proplegmatium and crepis is much longer than in any other species.

In males, the apices of parameres are elongate, large and only slightly hooked in H. acutus , H. bituberculatus and H. fallax , and more slender in H. depressus . In H. laceratus , the parameres of the aedeagus are narrower than in the other Hamonthophagus , rounded at the apex and slightly downcurved. The small, rounded ventral expansion is well developed mainly in H. laceratus (see Fig. 7 for a comparison among the species).

The primary lamella of the endophallus is elongate with a large hook at the base in H. acutus , H. bituberculatus , H. depressus and H. fallax , with small differences in the longitudinal development among these species. In H. laceratus the primary lamella is more peculiar, being tougher and half as long as in the other species, but always hook-shaped (see Fig. 8 for a comparison among the species).

These species can also be easily identified by the shape of the peculiar asymmetrical, funnel-shaped sclerotization of the vagina that shows a characteristic and differentiated development in the five species (see Fig. 10 for a comparison among the species).

General remarks: No preimaginal stages have been described so far.

Distribution: The genus Hamonthophagus is distributed in arid and savannah Afrotropical regions ( Fig. 14).

Etymology: The new genus was named after the Latin word hamo (= hook), with reference to the characteristic shape of the primary lamella of the internal sac.