Sinonichnus leiodicornutus, Jałoszyński, 2021

Jałoszyński, Paweł, 2021, Sinonichnus gen. n. for Scydmoraphes yunnanensis Jałoszyński, and description of Sinonichnus leiodicornutus sp. n. (Coleoptera, Staphylinidae, Scydmaeninae), Zootaxa 4938 (4), pp. 487-496 : 492-494

Sinonichnus leiodicornutus sp. n.

( Figs 2 , 5–10 , 12–16 )

Type material studied. Holotype ( China , Yunnan): ♁, two labels: “ CHINA mer.: Yunnan prov., / (pass SW from Baoshan / Gaoliging Shan) / 4. -8. 6. 2005, sifted from base of old tree / Oto Nakládal lgt.” [white, printed], „ SINONICHNUS \ leiodicornutus m. \ P. Jałoszyński, 2021 \ HOLOTYPUS “ [red, printed] ( MNHW).

Diagnosis. Body length slightly exceeding 1 mm; antennae in males conspicuously modified, with antennomere 7 strongly enlarged, slightly asymmetrical, with dorsal surface convex and ventral flat and covered with asperities forming irregular, partly concentric pattern; anterior margin of prosternum smooth, not crenulate; metaventrite in male with median elongate impression; aedeagus slender, with narrowly subtriangular apex, strongly elongate ventral diaphragm, endophallus lacking lateral bunches of needle-like sclerites.

Description. Body of male ( Fig. 2 ) flattened, light brown with indistinctly lighter appendages, covered with setae slightly lighter than cuticle; BL 1.05 mm.

Head ( Fig. 5 ) broadest at eyes, HL 0.18 mm, HW 0.20 mm; tempora in dorsal view indistinctly shorter than eyes; vertex and frons confluent, together weakly convex; each eye moderately large and weakly convex, with indistinct posteromedian emargination. Punctures on vertex and frons fine, inconspicuous; setae unequal in length, those on frons distinctly shorter than those on vertex, sparse, suberect. Antennae ( Figs 7–8 ) slender, AnL 0.40 mm, antennomeres 1 and 2 each elongate, 3–6 each distinctly transverse, 7 strongly enlarged and asymmetrical, dorsally convex and ventrally flat, with ventral surface ( Fig. 9 ) covered with asperities partly forming concentric pattern, and with small porous fields on smooth areas; antennomere 8 transverse, much shorter and narrower than 7; 9 and 10 each distinctly transverse, 11 shorter than 9–10 combined, only slightly longer than broad, with slightly asymmetrical, subconical distal region.

Pronotum ( Fig. 5 ) bell-shaped, broadest distinctly in front of middle; PL 0.28 mm, PW 0.25 mm. Anterior and lateral margins in anterior half strongly rounded, sides posteriorly weakly concave, basal margin barely discernibly bisinuate. Base with two pairs of small but distinct pits, inner pair connected by arcuate (anteriorly convex) groove; outer pits larger and diffuse; sides of pronotum with bristles inserted on papillate protuberances. Disc with fine, inconspicuous punctures; setae about as long, sparse and suberect as those on vertex.

Elytra ( Fig. 2 ) together oval, broadest clearly in front of middle; EL 0.60 mm, EW 0.39 mm, EI 1.55; humeral calli prominent, elongate, basal impressions large, deep, nearly circular; apices separately rounded. Punctures slightly more distinct than those on pronotum but still only superficial and inconspicuous; setae slightly longer and denser than those on pronotum, suberect.

Metaventrite ( Fig. 12 ) with large elongate longitudinal median impression flanked by setae denser than on remaining area; impression is asetose and nearly as long as median length of metaventrite.

Legs moderately long and slender, unmodified except for long ventral setae on protarsomeres ( Fig. 10 ).

Aedeagus ( Figs 13–16 ) strongly elongate, in ventral view about four times as long as broad; AeL 0.25 mm; median lobe in ventral view tapering distad, with elongate, slender subtriangular apex; endophallus with asymmetrical median tubular structure; parameres slender, each with one long apical seta.

Female. Unknown.

Distribution. China: Yunnan.

Etymology. The adjective leiodicornutus refers to the unusually modified antennae, which resemble those of many Leiodidae , with antennomere 8 short, but 7 and 9–11 long.

Remarks. Sinonichnus leiodicornutus differs from the previously known S. yunnanensis in the modified male antennae, smooth (not crenulate) anterior prosternal margin, a longitudinal median impression on the metaventrite flanked by setae denser than on sides, and a different form of the aedeagus.

Figures

FIGURES 1–2. Dorsal habitus of males. Sinonichnus yunnanensis Jałoszyński (1); Sinonichnus leiodicornutus sp. n. (2).

FIGURES 3–6. Morphological structures of Sinonichnus yunnanensis Jałoszyński (3–4) and Sinonichnus leiodicornutus sp. n. (5–6), males. Head, prothorax and elytral base in dorsal view (3, 5); head and prothorax in ventral view (4, 6). Abbreviations: abg, antebasal groove; abp, antebasal pit; bef, basal elytral fovea; bst, basisternal region of prosternum; hr, hypostomal ridge; hyr, hypomeral ridge; ihy, inner region of hypomeron; lpg, lateral pronotal groove; mn, mentum; ohy, outer region of hypomer- on; pgs, pre-tentorial gular suture; ptp, posterior tentorial pit; smn, submentum.

FIGURES 7–10. Morphological structures of Sinonichnus leiodicornutus sp. n., male. Left antenna in dorsal view (7); anten- nomeres 4–11 of right antenna in ventral view (8); ventral surface of antennomere 7 (9); distal region of left fore leg in dorsal view (10).

FIGURES 11–12. Morphological structures of Sinonichnus yunnanensis Jałoszyński (11) and Sinonichnus leiodicornutus sp. n. (12), males. Pterothorax and abdomen in ventral view (11); and pterothorax in ventral view (12). Abbreviations: msvp, mesov- entral intercoxal process; mtvp, metaventral intercoxal process; pcr, procoxal rest.

FIGURES 13–16. Aedeagus of Sinonichnus leiodicornutus sp. n. in ventral (13, 15) and lateral (14, 16) views.