Onthophagus dissidentatus Krikken & Huijbregts

Krikken, J. & Huijbregts, J., 2013, New Guinea Onthophagus: taxonomy of ten small, unicolored new species (Coleoptera: Scarabaeidae: Scarabaeinae), Zootaxa 3619 (5), pp. 501-525 : 515-516

Onthophagus dissidentatus Krikken & Huijbregts , new species

( Figs. 11, 22–23 , 80–88 )

Type material. Holotype male (CMNC) from PNG: Brown River, 30 mi N Port Moresby, 900 m, 15–16.vi.1974, S. Peck. Paratypes in listed Appendix 1.

Diagnosis. Clypeal apex bidentate, major males have their denticles set on short, strongly reflexed lobe (emargination between denticles not going down to base of lobe), on either side not delimited by sinuate border (as in O. kokodentatus ); clypeopleuron angulate below, in axial view. Frons in both sexes with pair of protrusions between anterior part of eyes, which are very slight in females; in major males these take the form of subconical tubercles. Females with fine, straight, transverse clypeofrontal ridge (not reaching clypeal sides). This species is usually shiny black or brown (may have metallic lustre); most of dorsum finely punctate, punctation varying in strength. Eye foramina narrow. Pronotum entirely evenly convex, lateral and basal borders evenly, widely rounded. Pygidium simply punctate. Proximal serrate section of protibia with approximately 8 small denticles. Body length usually 4–5 mm.

Description (holotype, male). Body length approximately 4.5 mm. Habitus convex, dorsum slightly deplanate. Color largely dark-brown, shiny, underside and legs medium-brown. Dorsum with abundant, scattered, fine punctation, lacking distinct setae or shorter bristles, underside with numerous pale-brown bristles and longer setae.

Head brown, entirely finely, sparsely to abundantly punctate, punctures on flat part of frontal disc sparse, minute. Clypeal border very widely rounded from uninterrupted clypeogenal transition to broadly reflexed, bidentate anterior margin, tips of denticles short, on upright, short lobe, margin on either side not sinuate (lobe angulate below, axial view); clypeogenal suture vague; clypeofrontal transition without elevation. Genal tip fully rounded, posterior extension tapering, reaching occipital side. Frontal surface between anterior part of eyes with pair of subconical tubercles, slight away from edge of eyes. Eye foramina very narrowly subelliptic, with approximately 8 facet rows across widest point. Ratio interocular distance / maximum eye width approximately 12.

Pronotum virtually black, shiny, with scattered, sparse to abundant, fine punctation; surface evenly, strongly convex (lacking midline impression); anterior declivity gradual, unmodified; anterior and lateral borders finely marginate; base extremely finely marginate; anterior section of lateral border almost straight (full-face view), anterolateral angle shortly rounded, subrectangular (full-face view); posterior section of lateral border very widely rounded (full-face view), without angle continuing to basal border; pronotal lateral and basal borders widely rounded in dorsal view

Elytra dark-brown, shiny; scutellum indistinct, shape of base and apex unmodified; epipleuron glabrous, brown, matt. Elytra broad, with 8 fine, distinct, straight to slightly curved, striae; stria 7 evenly, very slightly curved in front, ending at humeral umbone; strial punctures fine, on disc mostly separated by 5–7 puncture diameters, slightly crenulating interstriae. Interstrial surfaces slightly convex, with scattered, sparse, minute, simple punctation.

Antennal club light-brown, scapus unmodified. Mentum shallowly emarginate in front. Postocular area of propectus slightly concave, matt, posteriorly delimited by simple coxal-marginal ridge. Propectoral sides with several vague seta-bearing punctures. Metasternum moderately shiny, anterior lobe convex in front; metasternal disc with slight midline impression, very finely, abundantly punctate; metasternal flanks shiny, with numerous small, seta-bearing ocellate punctures. Abdominal ventrites shiny, each with more or less distinct row of setabearing punctures. Pygidium with general surface evenly convex, shiny brown, abundantly, finely punctate; base with transverse ridge, apex broadly marginate.

Legs slender, generally shiny brown. Protibia robust, with 3+1 larger external denticles (distal 3 long, slender, acuminate, proximal one small but distinct), distinctly separated by serration; proximal serration consisting of 8 small denticles; apico-external denticle oblique to tibial axis; apico-internal angle unmodified, terminal spur fine, long, tapering, slightly curved; protibial underside with low longitudinal crest; protarsus slender. Profemur robust, underside shiny, with numerous (partly seta-bearing) fine punctures. Mesofemoral and metafemoral undersides with numerous minute punctures. Mesotibiae and metatibiae slender, dilated distad to transversely subelliptic crest, which is fringed with short fossorial spines below, and some long, fine spines above; externally with approximately 3 slight, spine-bearing fossorial protrusions; mesotibia slightly sinuate internally. Mesotarsi and metatarsi generally slender, with fine sickle-shaped claws; mesotarsomeres and metatarsomeres 1 long, straight, unmodified. Terminal spurs on mesotibiae and metatibiae long, tapering. Length proportions terminal spur // metatarsomeres 1–5 in approximate integers: 7//8/4/2/2/3 (paratype male).

Parameres long, with tips simply tapering, curved downward, Fig. 22–23 .

Measurements in mm (dorsal view). Maximum width of head 1.4. Median length of pronotum 1.6 (base to tip of protrusion), maximum width 2.4. Sutural length of elytra 1.8, maximum width combined 2.5.

Variation and sexual dimorphism. Development of clypeal denticles varies, in minor males not distinctly set on lobe; in such males interocular denticles may be reduced to oblique swellings, as in females. Females have tips of clypeal denticles rounded off, more or less bisinuate; they have a fine, straight, transverse clypeofrontal ridge, laterally not reaching clypeogenal border. Female clypeus transversely rugulate. Body color varies, usually black, but occasionally brown, with or without metallic lustre. Body length 3–5 mm.

Etymology. Name is a contraction, referring to clypeal dentation being dissimilar from O. kokodentatus .

Figures

FIGURES 13 – 24. Parameres (lateral view) of Onthophagus species. 13, O. acerus, holotype; 14, O. aceroides, holotype; 15, O. baiyericus, holotype; 16, O. daymanus, holotype; 17, O. kokopygus, holotype; 18, O. kokocellosus, holotype; 19, O. bituberoculus, holotype; 20, O. kukali, holotype; 21, O. kokodentatus, holotype; 22 – 23, O. dissidentatus, paratype, Wau (22), paratype. N Port Moresby (23); 24, O. ofianus, holotype. Scale lines (on top of relevant parameres) equal 0.5 mm.

FIGURES 74 – 91. Onthophagus species, body parts. 74 – 79, O. kokodentatus, holotype (73 – 78), female paratype Iora Creek (79); 80 – 85, O. dissidentatus, holotype (80 – 84), female paratype N Port Moresby (85); 86 – 91, O. ofianus, holotype (85 – 89), female paratype Manari (91). Head (full-face) 74, 79, 80, 85, 91; pronotum (dorsal) 75, (dorsal, with rear view of frontovertexal protrusions) 81, 87; left elytron (dorsal) 76, 82, 88; protibia (upper side) 77, 83, 89; metatibia (underside) 78, 84, 90. Scale lines equal 1 mm.