Euconnus (Rhomboconnus) bicarinatus, Jałoszyński, 2020

Jałoszyński, Paweł, 2020, Euconnus (Rhomboconnus): redescriptions of species described by Schaufuss and Sharp, and descriptions of five new Mexican species (Coleoptera, Staphylinidae Scydmaeninae), Zootaxa 4759 (2), pp. 209-222 : 218-219

Euconnus (Rhomboconnus) bicarinatus sp. n.

( Figs 6 , 13 , 39–43 )

Holotype: Mexico (Veracruz State): ♂, two labels: “MEX: Ver: 33 km NE / Catemaco, 160 m / Los Tuxtlas Bio- Sta. / 1.VIII.83, S & J Peck / rav. litter & foungi [sic!]” [white, printed], “ EUCONNUS / ( RHOMBOCONNUS ) / bicarinatus m. / P. Jałoszyński, 2020 / HOLOTYPUS ” [red, printed] ( MHNG).

Diagnosis. Head in male stout, with broad and weakly arcuate posterior margin of vertex; tempora nearly straight and weakly narrowing posterad up to posterior fourth, where they are rapidly bent mesad; pronotum subconical with relatively broad anterior margin and rounded sides, broadest near posterior 1/4, with sharply marked transverse antebasal groove indistinctly deepened at each end and with conspicuously well developed sublateral carinae, which extend from posterior to anterior pronotal margin; pronotum with large round anteromedian impression on disc; dorsum sparsely setose; antennomere VII strongly, and VIII–X weakly elongate; aedeagus with ventral plate in distal half nearly rod-like, parallel-sided and narrow; endophallus with long and broad sclerites, of which the longest is pointed at apex, with asymmetrical distal portion.

Description. Body of male ( Fig. 6 ) moderately strongly convex, elongate, with moderately long and slender appendages, BL 1.80 mm; cuticle glossy, moderately dark brown, vestiture slightly lighter than cuticle.

Head ( Fig. 13 ) stout, weakly narrowing posteriorly, broadest at eyes, HL 0.40 mm, HW 0.35 mm; vertex and frons confluent, together evenly convex, except for a pair of shallow and diffuse longitudinal impressions on vertex just behind the level of eyes, posterior margin of vertex broad and weakly arcuate, with shallow and diffuse impression at middle; tempora nearly straight up to posterior fourth, where they are rapidly bent mesad, only slightly more than twice as long as eyes in dorsal view; supraantennal tubercles barely marked; eyes moderately large, finely faceted and relatively strongly projecting from silhouette of head. Punctures on vertex and frons fine and inconspicuous; setae relatively numerous, conspicuously short but discernible under magnification 100 ×, recumbent, additionally posterior portion of each temple with groups of dense thick setae. Antennae slender and relatively long, AnL 1.13 mm; antennomeres I–II strongly elongate, III slightly transverse, IV–X each elongate (VII the longest), XI nearly as long as IX–X together, 2.3 × as long as broad; antennomeres X and XI slightly flattened.

Pronotum ( Fig. 13 ) in dorsal view approximately subconical with relatively broad anterior margin, broadest near posterior fourth and weakly narrowing anterad, PL 0.43 mm, PW 0.43 mm; sides weakly rounded, anterior and posterior margins nearly straight, base with sharply marked transverse groove indistinctly deepened at each end, and with sublateral carinae forming step-wise ridges along entire lateral margin, with elongate area laterad each ridge distinctly impressed; anterior half or pronotal disc with shallow and diffuse round anteromedian impression. Punctures inconspicuous; disc covered with similar setae as those on head, but slightly sparser, additionally sides with long and dense thick bristles.

Elytra together suboval, broadest slightly in front of middle, EL 0.98 mm, EW 0.78 mm, EI 1.26; apices round- ed together. Punctures on elytral disc slightly more distinct than those on head and pronotum but superficial and inconspicuous; vestiture virtually absent (indiscernible under magnification 100 ×).

Legs moderately long and slender; unmodified.

Aedeagus ( Figs 39–43 ) stout, AeL 0.48 mm, in ventral view drop-shaped with apical region rapidly narrowed; endophallus with relatively broad complex of sclerites ( Fig. 43 ), of which the longest is asymmetrical in apical region, with slender, pointed apex; parameres slender, each with three long apical and subapical setae.

Female. Unknown.

Distribution. Southern Mexico.

Etymology. The adjective bicarinatus refers to the unusually long sublateral carinae.

Remarks. The unusual shape of head, long sublateral pronotal carinae and the anteromedian impression on the pronotum allow for unambiguous identification of this remarkable species.

Figures

FIGURES 1–8. Dorsal (1–3, 5–8) and lateral (4) habitus of Euconnus (Rhomboconnus). Euconnus cavifrons (L.W. Schaufuss) (1); E. giraffa Sharp (2); E. agiraffa sp. n. (3–4); E. oaxacanus sp. n. (5); E. bicarinatus sp. n. (6); E. cordobanus sp. n. (7); E. maya sp. n. (8).

FIGURES 9–15. Head and pronotum of Euconnus (Rhomboconnus) in dorsal view. Euconnus cavifrons (L.W. Schaufuss) (9); E. giraffa Sharp (10); E. agiraffa sp. n. (11); E. oaxacanus sp. n. (12); E. bicarinatus sp. n. (13); E. cordobanus sp. n. (14); E. maya sp. n. (15). Abbreviations: ami, anteromedian impression; abg, antebasal groove; abp, antebasal pit; slc, sublateral carina.

FIGURES 34–43. Aedeagus in ventral (34, 36, 39, 41) and lateral (35, 37, 40, 42) views, and endophallic sclerites in ventral view (38, 43) of Euconnus (Rhomboconnus). Euconnus oaxacanus sp. n. (34–38); E. bicarinatus sp. n. (39–43).