Sinonichnus, 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 : 488-490

Sinonichnus gen. n.

Type species: Scydmoraphes yunnanensis Jałoszyński, 2019 (here designated).

Diagnosis. Body elongate, with distinct constriction between head and pronotum and between pronotum and elytra; thick bristles present only on prothorax; head short and round, with eyes situated closer to mandibular bases than to occipital constriction, and with distinct tempora weakly convergent posterad; antennal fossae broadly separated at middle; antenna with indistinctly demarcated trimerous club; frontoclypeal groove lacking; posterior margin of vertex nearly straight and not bulging posterodorsad; submental region demarcated laterally by pre-tentorial gular sutures with broadly separated posterior ends, area between sutures elongate and subtrapezoidal; hypostomal ridges extending posteromesad and connecting to pre-tentorial gular sutures near middle; pronotum bell-shaped, broadest in front of middle; pronotum with two pairs of antebasal pits, inner pair connected by transverse groove; sides of pronotum with long longitudinal grooves, and with relatively blunt but distinct lateral pronotal carinae in posterior half; prosternum with narrow, carinate prosternal process in natural position hidden between procoxae; basisternal region slightly shorter than coxal area; notosternal sutures largely obliterated, visible only as short notches at anteroventral margin of prothorax; procoxal cavities closed by postcoxal prosternal lobe fused with postcoxal mesal lobe of hypomeron; hypomeral ridges present and complete, each accentuated by longitudinal lateral groove; mesoventral intercoxal process carinate, narrow and extending behind mesocoxae where it is fused with metaventrite; metaventral intercoxal process composed of pair of narrow pointed spines narrowly separating metacoxae; each elytron with two small but distinct and asetose basal foveae; aedeagus with symmetrical median lobe and partly asymmetrical endophallus, and with free, slender parameres.

Description. Body form ( Figs 1–2 ) elongate, slender, flattened, with distinct constrictions between head and pronotum and between pronotum and elytra.

Head ( Figs 3–6 ) subtrapezoidal; large eyes in males situated only slightly closer to mandibular bases than to occipital constriction, in microphthalmous females clearly closer to mandibular bases; tempora distinct, weakly narrowing posterad; vertex not bulging posterodorsad, confluent with frons and with posterior margin nearly straight; sides of head and vertex lacking thick bristles. Occipital constriction about as broad as frons between eyes; ‘neck’ region slightly broadening posterad.Antennal fossae small and situated anterolaterally, broadly separated at middle. Frontoclypeal groove lacking; clypeus short, with parallel sides. Gular plate on ‘neck’ region of head transverse, with indistinct gular sutures which extend anteriorly beyond tentorial pits as pre-tentorial gular sutures ( Figs 4, 6 ; pgs) divergent anterad; posterior tentorial pits ( Figs 4, 6 ; ptp) barely discernible, tiny and nearly circular. Submentum ( Figs 4, 6 ; smn) subtrapezoidal; mentum ( Figs 4, 6 ; mn) subtrapezoidal, broadest slightly behind straight anterior margin; prementum largely membranous, flexible, with small papillate ligula bearing pair of anterior setae, with moderately broadly separated bases of labial palps; labial palpomere 1 short, ring-like, palpomere 2 elongate, subcylindrical, palpomere 3 narrow, elongate, tapering distad and straight. Maxilla ( Figs 4, 6 ) with large cardo, subtriangular basistipes, broad mediostipes, elongate lacinia and galea, each with robust setae along distomesal margin, palpifer elongate, maxillary palp with distinctly elongate palpomere 1, long, clavate and weakly curved palpomere 2, broad and relatively short palpomere 3 about 2.5 × as long as broad, and subconical palpomere 4. Mandibles poorly visible in studied specimens, symmetrical, each subtriangular, mesal margins not studied. Labrum strongly transverse, with rounded anterior margin, and with sparse, symmetrically distributed dorsal setae directed anterad.

Antenna ( Figs 1–2 , 7–9 ) slender, with scape and pedicel each elongate; short and loosely assembled antennomeres 3–8; and indistinctly demarcated trimerous club; in one species antennae in males modified ( Figs 7–9 ), with strongly enlarged antennomere 7, which is slightly expanding mesad and has its ventral surface flat and covered with asperities forming a nearly concentric pattern with several small porous fields on smooth areas ( Fig. 9 ).

Prothorax in dorsal view ( Figs 1–2 , 3, 5 ) bell-shaped, short, broadest slightly or distinctly in front of middle. Anterior and lateral margins confluent, without marked anterior angles; sides weakly sinuate behind the broadest site; posterior corners well-marked but blunt; posterior margin nearly straight. Pronotal base with two pairs of distinct pits ( Figs 3, 5 ; abp), inner pair connected by arcuate transverse groove ( Fig. 5 ; abg; in Fig. 3 poorly visible because of the ‘lighting’ angle, but well-visible under stereomicroscope). Sides of pronotum with moderately distinct lateral carinae in posterior half, deep longitudinal groove ( Figs 3, 5 ; lpg) at each side extending from outer antebasal pit to near anterior margin, and with thick bristles. Prosternum ( Figs 4, 6 ) nearly as long as half of prothorax, with basisternal region ( Figs 4, 6 ; bst) demarcated posteriorly by ridges of anterior margins of procoxal rests, laterally fused with inner regions of hypomera, so that notosternal sutures are largely obliterated, discernible only as notches at anteroventral margin of prothorax. Prosternal process developed as weakly elevated narrow carina in intact specimens hidden between procoxae; posterior margin of coxosternal region with deep median emargination. Hypomeral ridges complete, each accentuated by additional lateral (outer) groove, separating asetose inner region of hypomeron ( Figs 4, 6 ; ihy) and outer region ( Figs 4, 6 ; ohy) densely covered with thick bristles and sparse setae. Procoxal cavities broadly closed; postcoxal hypomeral lobe fused with postcoxal prosternal lobe.

Mesonotum with subtriangular scutellar shield about as long as broad, in natural position hidden under posterior margin of pronotum and not visible between elytral bases in intact specimens.

Mesoventrite ( Figs 11–12 ) transverse, with moderately long prepectus, transverse and partly setose anteromedian impressions functioning as procoxal rests ( Figs 11–12 ; pcr) separated at middle by longitudinal carina that posteriorly extends into narrow, carinate mesoventral intercoxal process ( Figs 11–12 ; msvp), its posteriorly end fused with metaventrite.

Metanotum not studied.

Metaventrite ( Figs 11–12 ) subrectangular, anteriorly fused with mesoventrite, lacking anterior metaventral process, with metaventral intermetacoxal process ( Figs 11–12 ; mtvp) composed of pair of long, slender and pointed spines narrowly separating metacoxae. Metanepisterna and metepimera fully demarcated and narrow.

Legs slender, lacking peculiar features, except for sexual dimorphism expressed in long setae covering ventral surface of protarsomeres in males ( Fig. 10 ).

Elytra ( Figs 1–2 , 3, 5 ) together oval, each with pair of small but distinct asetose basal foveae ( Figs 3, 5 ; bef).

Hind wings functional.

Abdomen ( Fig. 11 ) subtriangular, with six exposed sternites (sternites 3–8), suture between 7 and 8 indistinct.

Aedeagus ( Figs 13–16 ) with symmetrical median lobe, at least partly asymmetrical endophallic structures (especially tubular median elements) and rod-like parameres with apical setae.

Etymology. Sinonichnus combines Sino -, after Latinized China, with - nichnus derived from the genus name Stenichnus , to which the new genus is remotely similar. Gender masculine.

Composition and distribution. Sinonichnus comprises two nominal species, both known to occur in Yunnan, China.

Remarks. This is the only genus of Stenichnini with the pre-tentorial gular sutures that has the notosternal sutures obliterated, so that the prosternum is laterally fused with the inner region of each hypomeron. See also Discussion.

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.