Onthophagus bituberoculus 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 : 511-513

Onthophagus bituberoculus Krikken & Huijbregts , new species

( Figs. 8 , 19 , 58–62 )

Type material. Holotype male (MBBJ) from Indonesia: Irian Jaya: Freeport Concession, 11.iii.1997, R. Ubaidillah, Dpt 5-5 97206, dry lowland forest, 4˚ 26’ 21” S–136˚ 52’ 59” E, 300 ft, dung pitfall trap. Paratypes listed in Appendix 1.

Diagnosis. A quasi outsider in the group with large eye foramina by having a fine but distinct clypeofrontal ridge and an interocular pair of (albeit low) conical protrusions. Genal border fully, evenly rounded, seemingly short, but posteriorly connected to occipital side by fine, pigmented line. Color varying from yellow to mediumbrown (one black male may represent a different species, see Comments, below). Dorsum shiny, punctation generally superficial, poorly defined, somewhat more distinct and denser on pronotum; interstrial punctation very vague, minute. Eyes very broadly elliptic, separated over frons by about two eye-widths. Clypeal apex shallowly bisinuate, margin slightly reflexed. Pygidium scattered with punctation varying in size, several punctures with long seta. Comparatively large, body length usually 5–7 mm.

Description (holotype, male). Body length approximately 6.5 mm. Habitus convex, dorsum deplanate. Color largely medium-brown, shiny (vaguely shagreened), underside and legs lighter brown. Dorsum with fine, superficial punctation, most distinct on pronotum, lacking distinct setae or shorter bristles, underside with numerous pale-brown bristles and longer setae.

Head brown, frons lacking distinct punctation, virtually smooth, genae with some indistinct punctures. Clypeogenal border widely, evenly rounded from genal side to slightly reflexed, bisinuate clypeal apex; clypeogenal transition continuous at border, suture vague; clypeofrontal transition with distinct, low, slightly arcuate transverse ridge reaching clypeogenal suture; clypeal surface superficially, transversely rugulate. Genal tip fully rounded, posterior extension tapering to fine dark line, reaching occipital side (i.e., eyes laterally quasiundivided). Frontal surface halfway eyes with pair of small conical tubercles, close to eye border. Eye foramina very broadly elliptic, with approximately 21 facet rows across widest point. Ratio interocular distance / maximum eye width approximately 2.1.

Pronotum brown, shiny with scattered, with sparse to abundant, fine, shallow, poorly-defined punctation (qualification depending on angle of view); surface evenly convex (lacking midline impression); anterior declivity gradual, unmodified; all borders finely marginate; anterior section of lateral border almost straight (full-face view), anterolateral angle shortly rounded, subrectangular; posterior section of lateral border slightly sinuate (full-face view), almost straight in dorsal view, posterolateral angle rounded off, continuing to basal border; basal border of pronotum widely rounded in dorsal view, with vague median angle.

Elytra brown, shiny; scutellum indistinct, shape of base and apex unmodified; epipleuron with seta-bearing punctures, light brown, shiny. Elytra broad, with 8 fine, distinct, straight to slightly curved, striae; stria 7 evenly, slightly sinuate in front, ending on humeral umbone; strial punctures fine, on disc mostly separated by 6–10 puncture diameters, slightly crenulating interstriae. Interstrial surfaces slightly convex, with scattered, sparse, minute, simple, superficial punctation.

Antennal club yellow, 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 fine seta-bearing hemi-punctures, setae subappressed. Metasternum moderately shiny, anterior lobe slightly, evenly convex in front; metasternal disc damaged by needle; metasternal flanks matt, with numerous fine, seta-bearing ocellate punctures. Abdominal ventrites matt, each laterally with row of small, superficial seta-bearing punctures. Pygidium with general surface evenly convex, light brown, matt, with numerous punctures of different sizes, several with seta; base with transverse ridge, sides and apex distinctly 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 6 small denticles; apico-external denticle oblique to tibial axis; apico-internal angle unmodified, terminal spur fine, elongate-acuminate, curved; protibial underside with low longitudinal crest; protarsus slender. Profemur robust, underside shiny, with numerous (partly seta-bearing) punctures. Mesofemoral and metafemoral undersides with fewer punctures, very few with seta. Mesotibiae and metatibiae slender, dilated distad to transversely subelliptic crest, which is fringed with short fossorial spines below, and some longer spines above; externally with approximately 5 sets of very slight, spine-bearing fossorial protrusions; mesotibia slightly sinuate. Mesotarsi and metatarsi generally very slender, with distinct sickle-shaped claws; mesotarsomeres and metatarsomeres 1 long, virtually straight, unmodified. Terminal spurs on mesotibiae and metatibiae elongate-acuminate. Length proportions terminal spur // metatarsomeres 1–5 in approximate integers: 15// 18/7/4 /3/6.

Aedeagus distorted; parameres broad at base, short, each with strongly tapering stalk (full-face view), curved downward (lateral view), Fig. 19 .

Measurements in mm (dorsal view). Maximum width of head 2.0. Median length of pronotum 2.1, maximum width 3.2. Sutural length of elytra 3.0, maximum width combined 3.8.

Variation and sexual dimorphism. Females very similar to male holotype, any differences gradual and minimal. General color varies from yellow through medium brown to black (see also Comments, hereafter). Body length 5–7 mm.

Comments. Three light brown to medium brown females and a single male from two regions of West New Guinea are referred to O. bituberoculus . In spite of the male specimen being poorly cohesive, the parts being a bit loose, it is designated holotype; caution: aedeagus of this holotype very weakly sclerotized, fragile, and contours in Fig. 19 may be distorted.

In Papuasia and elsewhere, in the Moluccas and Sundaland, more relatives of O. bituberoculus occur, some unnamed (and not listed here) because only inadequate singletons are available. An example is a small, black male from Papua New Guinea (vicinity of Wau), basically similar to O. bituberoculus (i.e., with clypeofrontal ridge), here illustrated (head, Fig. 62 ); excluded from the type series.

Etymology. Name is a contraction, referring to pair of tubercles between eyes.

Figures

FIGURES 1 – 8. Habitus (oblique view) of Onthophagus species, with indication of body length. 1, O. acerus, holotype ,, 6 mm; 2, O. aceroides, holotype, 5 mm; 3, O. baiyericus, holotype, 5 mm; 4, O. mimikanus, female holotype, 6 mm; 5, O. kokopygus, holotype, 3 mm; 6, O. daymanus, holotype, 4.5 mm; 7, O. kokocellosus, holotype, 4.5 mm; 8, O. bituberoculus, female paratype, Timika, 7 mm.

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 58 – 73. Onthophagus species, body parts. 58 – 62, O. bituberoculus, holotype; 63, O. bituberoculus (or near), male; 64 – 68, O. kokocellosus, holotype; 69 – 73, O. kukali, holotype. — Head (full-face) 58, 63, 64, 69; pronotum (dorsal) 59, 65, 70; left elytron (dorsal) 60, 66, 71; protibia (upper side) 61, 67, 72; metatibia (upper side) 62, (underside) 68, 73. Scale lines equal 1 mm.