Hlavaciellus sumatranus Jałoszyński 2021, sp. n.
Creators: name: Jałoszyński, Paweł
Publisher: name: Zenodo
Year: 2021
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Staphylinidae
Hlavaciellus
Hlavaciellus sumatranus

description: Hlavaciellus sumatranus sp. n.
(Figs 21–25)
Type material. Holotype: INDONESIA (Sumatra): ♂, two labels: “ SUMATRA: Jambi / Mt Kerinci, 3300 m, 12.XI.1989 / Agosti, Löbl / Burckhardt #12a” [white, printed], “ HLAVACIELLUS / sumatranus m. / P. Jałoszyński, 2021 / HOLOTYPUS” [red, printed] (MHNG).
Diagnosis. Body large, exceeding 2 mm in length; head in males modified: posteromedian region of vertex with group of dense setae forming loose tuft, vertex with shallow transverse postocular impression, and posterior margin of frons behind each supraantennal tubercle with arcuate (posteriorly convex) ridge; each of antennomeres 3–9 elongate, 10 about as long as broad; aedeagus in ventral view slender, nearly 4 times as long as broad and distinctly narrowing both toward apex and base; parameres with thin subapical setae and rapidly narrowed apical portions.
Description. Body of male (Fig. 21) stout, strongly convex, uniformly dark brown; setae distinctly lighter than cuticle; BL 2.18 mm.
Head (Fig. 22) broadest at large, strongly convex and coarsely faceted eyes, HL 0.38 mm, HW 0.58 mm; posteromedian region of vertex with group of dense setae forming loose tuft, vertex with shallow transverse postocular impression, and posterior margin of frons behind each supraantennal tubercle with arcuate (posteriorly convex) ridge. Frons between supraantennal tubercles with uneven, slightly coarse surface; punctures on remaining areas fine and inconspicuous; setae long, moderately dense and suberect, those on posteromedian region of vertex dense and erect, postocular impression asetose. Antennae slender, AnL 1.38 mm, BL/AnL 1.58; scape indistinctly elongate, pedicel as long as broad, antennomeres 3–7 each strongly elongate, 8 and 9 each slightly elongate, 10 about as long as broad, 11 indistinctly shorter than 9–10 combined, twice as long as broad.
Pronotum subrectangular, equally broad between base and anterior third; PL 0.68 mm, PW 1.00 mm, PI 0.68; anterior margin weakly rounded; sides with finely crenulate lateral carinae, in posterior 2/3 straight; posterior corners right-angled and with blunt tips; posterior margin shallowly bisinuate; pronotal disc strongly convex, with area at each posterior corner distinctly impressed; antebasal pits slightly closer to posterior than to lateral margins. Punctures on pronotum fine and inconspicuous; setae long, dense, suberect.
Elytra together oval, broadest distinctly in front of middle; EL 1.13 mm, EW 0.98 mm, EI 1.15; subhumeral lines sharply marked, each developed as step-wise border between elevated humeral region and median area, as long as 0.3 EL; sides of elytra strongly rounded; elytral apices separately rounded. Punctures and setae similar to those on pronotum.
Legs long and slender, unmodified.
Aedeagus (Figs 23–24) elongate and slender; AeL 0.40 mm; median lobe in ventral view nearly 4 times as long as broad, broadest near sub-basal third and with broadly rounded sides; endophallic structures in the only known specimen erected, darkly sclerotized and tubular; parameres with thin subapical setae, each with parallel-sided and then rapidly narrowed distal region.
Female. Unknown.
Distribution. Sumatra (Fig. 25).
Etymology. After terra typica, i.e., Sumatra.
Remarks. Apart from unique modifications of the head, the only known male of H. sumatranus has the pronotum distinctly broader than elytra, a feature not known in any other congener described so far. Although the aedeagus of the holotype is in erected condition, with endophallic structures projecting distally from the ostium, the shape of parameres in lateral view can be used as one of diagnostic characters. The apical region of each paramere resembles that of the sympatric H. concavus, but in the latter species the parameres are weakly, and in H. sumatranus strongly curved near distal third.
description: Published as part of Jałoszyński, Paweł, 2021, Six new species of the Oriental genus Hlavaciellus Jałoszyński (Coleoptera Staphylinidae, Scydmaeninae), pp. 1-15 in Zootaxa 4966 (1) on pages 10-11, DOI: 10.11646/zootaxa.4966.1.1, http://zenodo.org/record/4729328