Taxonomy of new relatives of Onthophagus catenatus Lansberge, 1883 from New Guinea (Coleoptera, Scarabaeidae, Scarabaeinae)

Abstract Four new taxa from New Guinea are proposed in the dung beetle genus Onthophagus Latreille, 1802, all in the operational group of Onthophagus catenatus Lansberge, 1883. The group is discussed, defined, and the five taxa included are listed, keyed, and diagnosed. Three new species are described: Onthophagus abmisibilus (from West New Guinea, Indonesia), Onthophagus kokodanus, Onthophagus kokosquamatus (both from Papua New Guinea). One new species comprises a lowland and an upland subspecies: Onthophagus kokodanus kokodanus and kokodanus hagenaltus (both in Papua New Guinea).


Introduction
The onthophagine dung beetle fauna of New Guinea and nearby islands has been the subject of various recent papers, including a general discussion with descriptions of a diverse array of new species (Krikken & Huijbregts 2012), and a separate treatment of small, unicolour new species (Krikken & Huijbregts in press), all in the subcosmopolitan mega-genus Onthophagus Latreille, 1802. The present paper deals with four new species-group taxa similar to the New Guinea Onthophagus catenatus Lansberge, 1883 in features of their vertexal armature, size range, and various other characters. Major males in this operational group have a vertexal pair of long, evenly curved, laterally directed horns, lacking accessory inward lobes and denticles; they differ from the members of the closely related O. tauroides Gillet, 1930, group (cf. Krikken & Huijbregts 2012 by the horns at their base being distinctly contiguous, showing a low, variably shaped but relatively simple interconnecting elevation. The pronotum may be slightly modified (depressed, bluntly bifid, etc.), but never with deep concavities and/or strong, sharp protrusions. Note that the material available is limited, particularly from a geographic point of view, and therefore this paper should, after the last overview of Balthasar (1969), be considered just another partial update, attempting to make more taxonomic sense of the morphological diversity now seen in this set of Onthophagus species.
This Onthophagus catenatus group as here conceived is indeed diverse, and the group concept may even be insufficiently inclusive, as will be clear from the comments below. Formal group delimitation and species identification are, as usual among Scarabaeinae, complicated by intraspecific polymorphism -males, for instance, may look like females, and some species (here excluded) may never have males with long, curved, laterally directed horns. One form (O. kokodanus kokodanus subsp. n.) has an isolated conical median tubercle just in front of the base of its broad male vertexal horns, possibly the result of a morphoclinal forward-shifting of the medially angulate interconnecting ridge seen in other group members. Another species (O. kokosquamatus sp. n.) has a peculiarly rugulate-squamate pronotal surface and unusual lateral pronotal margins. This species stands apart from the others, and may be related to two much smaller named species here excluded from the catenatus group (see Comments under O. kokosquamatus). Both sexes of O. kokosquamatus have a similar, usually welldeveloped vertexal armature, contrary to at least two of the other species, in which the vertexal armature of females is reduced to a simple or more complex transverse ridge, its shape apparently different according to species.
The key to the species given below takes all this into account, the first couplet firmly delimiting the catenatus group from other Papuasian Onthophagus with long horns, in spite of the afore-mentioned complications. Onthophagus catenatus Lansberge, 1883, is apparently a widespread species, the label data we have seen indicate a range of altitudes from the Aru Islands to the Mount Hagen highlands and beyond. Although there is some variation, certainly needing further study, our present concept of the species (cf. also Comment in species account) is consistent with van Lansberge's (1883) description, which mentioned the characteristic strengthening of the punctures in the elytral striae, from base to apex.
All four species included in the Onthophagus catenatus group are formally placed in the nominotypical subgenus.

Material and methods
The material used in this work mainly comes from the Canadian Museum of Nature (Ottawa), and comprises 5 species-group taxa, 22 collection records, 166 specimens. The data given in the lists closely follow the information on the specimen labels. Paratypes, where available in sufficient numbers, will in due course be distributed to other collections.
Body part measurements in the descriptions were taken through the microscope with a calibrated ocular scale, and rounded off to 0.1 mm; approximate total body lengths (given for specimens as is) rounded off to ½ mm. For more background, references, and terminological and technical matters, see our companion papers mentioned above. One terminological addition: hemi-punctures are those that have about half of their peripheral rim effaced, usually having a seta more or less decumbent to the effaced side. Diagnosis. Male of this species has two very distinctive features: the concave (in axial view), non-angulate crest of the plate connecting the bases of the vertexal horns, and the rather flat, faintly metallic anterior declivity of the pronotum. Dorsum black-brown, largely matt (particularly elytra). Elytral strial punctures all distinct, fine, equal-sized, and only slightly crenulating interstriae. Lateral border of pronotum distinctly rounded at some distance from anterolateral angle. Pronotum with widely bisinuate, blunt crest behind anterior declivity. Clypeofrontal ridge low, almost straight, on either end angularly connected at clypeogenal ridge. Most of dorsal side finely to minutely, sparsely punctate. Clypeal tip broadly, slightly reflexed, apical border bisinuate. Dorsal eye parts broadly elliptic, separated by slightly over three eye-widths. Pygidium abundantly, finely, distinctly punctate. Body length ca 11.5 mm, O. catenatus being smaller, 8-10 mm.
Head shiny, sparsely micropunctate throughout. Clypeal border broadly, distinctly marginate, sides very slightly rounded (almost straight) from genae to apex, the latter bisinuate, slightly reflexed, shortly lobiform; clypeogenal transition at border very obtusely angular, on either side with almost straight ridge extending past end of very weakly curved, distinct clypeofrontal ridge onto frontal side. Genal border evenly, widely rounded. Vertex between posterior end of eyes with pair of long, basally broad horns, connected at base by transverse, slightly concave, laterally sinuate (plate-like) elevation (in axial view); horns widely, evenly arcuate upward, directed laterad, over and beyond eyes (in axial view), evenly tapering to blunt tip; distal section of horn rounded on all sides. Frontal disc limited by fine frontogenal ridge, on either side extending along eye. Dorsal eye parts widely elliptic, with ca 28 facet rows across widest point. Ratio of interocular distance to maximum (transverse) eye width ca 3.3.

Onthophagus catenatus
Comment. A male in the Gillet drawers of the IRSNB, agreeing with van Lansberge's (1883) description, bears type label and originates from the region mentioned in the original description (northern New Guinea) -it may be one of the syntypes.  Diagnosis. The pair of interconnected, basally broad (in axial view), plate-like vertexal horns in the major male, with the median conical tubercle just in front, constitutes the primary feature of this subspecies -at least in major males. Lateral border of pronotum distinctly rounded at about 0.4 of length behind anterolateral angle (not angular, in dorsal view, Fig. 34). Pronotum with blunt bisinuate rim behind broadly depressed, more or less concave anterior declivity, all this reduced in minors. Clypeofrontal ridge low, slightly arcuate, ends on either side angularly connected at clypeogenal ridge. Most of dorsal side finely to minutely, sparsely, evenly punctate. Clypeal tip distinctly, broadly reflexed, apical border bisinuate. Dorsal eye parts broadly elliptic, separated by slightly over three eyewidths. Elytra sericeous, virtually matt, sparsely micropunctate; strial punctures very fine, widely separated, all similar, not stronger caudad. Pygidium sparsely to abundantly, very finely punctate. Colour generally black-brown, moderately shiny, without metallic lustre. Body length usually 10-12 mm.
The presence of an isolated conical protrusion right in front of the horns is shared with other New Guinea species, like O. heurni Gillet, 1930 andjoliveti Paulian, 1973, which may be confusing. The males of both these species, however, have on their horns, which are more or less erect, a distinct basal-internal lobe or denticle, and their eyes are narrow.
Clypeal border broadly, distinctly marginate, sides virtually straight from genae to bisinuate, reflexed, shortly lobiform apex; clypeal surface shiny, with sparse, minute punctation; clypeogenal transition at border obtusely angular (anterolateral corner of gena slightly elevated), on either side with straight ridge to slightly arcuate, distinct clypeofrontal ridge. Genal and frontal surface minutely punctate as on clypeus; genal border evenly, widely rounded. Vertex between posterior end of eyes with pair of long, complanate, basally very broad horns, connected at base, with distinct conical tubercle medially on anterior side; horns strongly directed laterad (beyond eyes, in axial view), evenly curving upward to tapering, blunt tip, inner edge of horns sinuate (in axial view); horn surface also minutely, sparsely punctate. Frontal disc limited by fine frontogenal ridge, on either side extending along eye. Dorsal eye parts widely elliptic, with ca 28 facet rows across widest point. Ratio of interocular distance to maximum (transverse) eye width ca 3.2.
Pronotum generally strongly convex, surface shiny; disc posteriorly slightly convex (midline impression virtually effaced), anterior surface broadly depressed, medially shallowly concave up to posterior, strongly bisinuate, transverse protrusion coming from disc forward; anterior and lateral borders of pronotum marginate; anterior section of lateral border slightly concave; anterolateral angle rectangular, shortly rounded; posterior section of lateral border slightly sinuate, posterolateral angle rounded; base medially finely marginate along very obtuse basomedian angle. Most of pronotal surface finely, sparsely punctate, anterior depression minutely, sparsely punctate, this punctation interspersed with vague micropunctation.
Variability and sexual dimorphism. Strongly varying in the development of the vertexal armature. Females have a complex transverse vertexal ridge (Fig. 38), not the variably long horns like in males (note the minor male in Fig. 15, and beware of extremely minor males looking like females, as in the next subspecies). Female vertexal ridge with sides laterally obtusely angulate, thence sloping to eye, medially with robust knob; pronotum with pair of blunt, forward protrusions topping anterior declivity. Body length 9-12 mm.
Etymology. Name refers to the Kokoda Trail, the type locality; to be treated as masculine noun. Diagnosis. The vertexal horns of this subspecies are more upright, even in major males, with angular tubercle on top of the interconnecting basal ridge. Dorsum blackbrown, largely shining (particularly the elytra), with slight greenish metallic lustre. Elytral strial punctures all equally small, distinct, scatteredly crenulating finely punctate interstriae. Lateral border of pronotum distinctly rounded at about 0.4 of length behind anterolateral angle (not angular, in dorsal view, Fig. 40). Pronotum usually with blunt bisinuate rim behind depressed, medially more or less concave anterior declivity. Clypeofrontal ridge low, very slightly arcuate, ends on either side angularly connected to clypeogenal ridge. Most of dorsal side finely, sparsely punctate. Clypeal tip distinctly, broadly reflexed, apical border bisinuate. Dorsal eye parts broadly elliptic, separated by about three eye widths. Pygidium abundantly, finely, distinctly punctate. Body length usually 10-11 mm. Female unknown.
Apparently a close highland relative of the preceding subspecies. Description (holotype, male). Body length ca 11 mm. Habitus generally convex, robust. Colour of dorsal side black, generally shiny, with slight metallic lustre; ventral parts largely black, partly matt (microreticulate); legs black-brown, shiny. Dorsal side and pygidium virtually glabrous (apart from any inconspicuous micro-stubbles); ventral side and legs with numerous long, light-brown setae.
Clypeal border broadly, distinctly marginate, sides virtually straight from genae to bisinuate, reflexed, shortly lobiform apex; clypeal surface shiny, with sparse to abundant, minute punctation; clypeogenal transition at border obtusely angular, slightly elevated, on either side with straight ridge curving to end of virtually straight, distinct clypeofrontal ridge. Genal and frontal surface sparsely, minutely punctate; genal border evenly, widely rounded. Vertex between posterior end of eyes with pair of long, basally very broad horns, connected at base by angular ridge, with distinct anteromedian angle; horns slightly curved, directed upright behind eyes (not beyond, in axial view), evenly tapering to blunt tip, inner edge of horns evenly concave (in axial view); horn surface with convex anterior surface, minutely, sparsely punctate. Frontal disc limited by fine frontogenal ridge, on either side extending along eye. Dorsal eye parts widely elliptic, with ca 28 facet rows across widest point. Ratio of interocular distance to maximum (transverse) eye width ca 3.0.
Variability and sexual dimorphism. Female unknown; females probably have a transverse vertexal ridge, not the variably long horns of the males. Strongly varying: there is a minor male looking like a female, having a transverse vertexal ridge (Fig. 44), its aedeagus being similar to that of the holotype. Body length 9.5-11 mm.
Diagnosis. The strongly rugulate-punctate pronotum, with the peculiar squamiform texture on the anterior gibbosity, together with its large size, should distinguish O. kokosquamatus from its relatives, or for that matter, any known Papuasian congeners. Bases of both vertexal horns interconnected by robust ridge topped with distinct forward angle. Lateral margin of pronotum distinctly angular at about 0.4 of length behind anterolateral angle (Fig. 46). Pronotal surface behind horns with numerous long setae. Distinctly arcuate clypeofrontal ridge well developed, its ends on either side angularly connected at clypeogenal ridge. Clypeogenal border obtusely angular (full-face view). Clypeal tip distinctly, broadly reflexed, apical crest bisinuate. Dorsal eye parts elliptic, less broad than in the preceding species, separated by about 4.5 eye widths. Most of head surface abundantly, finely punctate; female clypeus transversely rugulate. Elytral interstriae on disc sparsely, indistinctly punctate, lateral interstriae more densely punctate; strial punctures very fine, widely separated, all similar. Pygidium very densely, distinctly punctate. Metasternum superficially prow-shaped in front, behind transverse rim. Colour generally black-brown, without any metallic lustre (elytra lacking reflections shifting in relation to angle of view). Male and female very similar. Body length usually 11-12 mm. For smaller potential relatives, cf. comments below.
Description (holotype, male). Body length ca 11.5 mm. Habitus convex, robust. Colour of dorsal side black, generally moderately shiny, forebody heavily (rugulate-) punctate; ventral parts largely black, partly shiny, strongly punctate; legs brown-black, shiny. Dorsal side and pygidium locally with some longer light brown setae (apart from inconspicuous micro-setae); ventral side and legs with numerous long, light-brown setae.
Clypeal border broadly, distinctly marginate, sides virtually straight from genae to apex, the latter bisinuate, reflexed, shortly lobiform; clypeal surface shiny, with abundant, fine punctation; clypeogenal transition at border obtusely angular, on either side with straight ridge to arcuate, very distinct clypeofrontal ridge. Genal surface finely, abundantly punctate as on clypeus, surface, like sides of clypeus, superficially transverse rugulate; genal border evenly, widely rounded. Vertex between posterior end of eyes with pair of long horns, which are convex in front, basally broad, and are connected at base by high, medially angulate ridge (axial view); horns strongly directed laterad (over eyes), evenly curving upward to tapering (on posterior side thickened) tip, their surface abundantly, very finely punctate. Frontal disc finely, abundantly punctate between slight genal sutures. Dorsal eye parts broadly elliptic, with 13-15 facet rows across widest point. Ratio of interocular distance to maximum (transverse) eye width ca 4.5.
Pronotum generally strongly convex; disc slightly convex (midline impression virtually effaced by heavy punctation); anteromedian surface strongly, evenly bulbous from disc forward; sides, behind horns of head, distinctly concave (with numerous long, decumbent setae), sloping down to anterolateral corner; anterior and lateral borders of pronotum marginate; anterior section posteriorly, at ca 0.4 of total length, with distinct angle, border very slightly concave; anterolateral angle rectangular, rounded; posterior section of lateral border strongly sinuate, posterolateral angle distinct; base medially slightly marginate along very obtuse basomedian angle. Most of pronotal surface densely rugulate-punctate, rugulation on anteromedian bulb squamiform (like reptile skin); anterolateral concavities largely smooth, many punctures on anterolateral surface looking like small horseshoes.