Euconnus (Rhomboconnus) plaumannioloides, Jałoszyński, 2017

Jałoszyński, Paweł, 2017, Euconnus (Rhomboconnus) of Panama (Coleoptera, Staphylinidae, Scydmaeninae), Zootaxa 4323 (1) : -

Euconnus (Rhomboconnus) plaumannioloides sp. n.

( Figs 1 , 9 , 17–18 , 25–26 , 49 )

Holotype: Panama (Coclé Province): ♂, two labels: " PANAMA, El Cope / 22/04/2014 / 8,670°N, 80,591°W / litter layer, leg. Tim Struyve" [white, printed], " EUCONNUS / ( RHOMBOCONNUS ) / plaumannioloides m. / P. Jałoszyński, '17 / HOLOTYPUS " [red, printed] ( MNHW). Paratype: ♀, " PANAMA, Cerro Azul / 14/05/2014 / 9,199°N, 79,395°W, / litter layer, leg. Tim Struyve" [white, printed], and standard yellow " paratypus " label ( TSCB).

Diagnosis. BL <1.8 mm; head, pronotum and elytra dorsally with very sparse setae; tempora weakly narrowing posteriorly and then rapidly bent mesally; pronotum broadest in posterior third and strongly narrowed posteriorly, sides slightly concave in anterior fourth; pronotum with a pair of ridges extending posterolaterally from each anterior corner, area lateral to each ridge distinctly impressed; pronotal base with transverse groove; parameres not broadened in subapical region.

Description. Body of male ( Fig. 1 ) strongly convex, elongate, with moderately long appendages, BL 1.76 mm; cuticle glossy, uniformly dark brown, vestiture slightly lighter than cuticle.

Head ( Fig. 9 ) weakly narrowing posteriorly, broadest at eyes, HL 0.40 mm, HW 0.33 mm; vertex and frons confluent, evenly and weakly convex except frons in front of eyes which steeply declines anteriorly, posterior margin of vertex projecting posteriorly as rounded lobe about as broad as 1/3 of HW; tempora nearly straight in anterior 3/4 and rapidly bent mesally in posterior fourth; supraantennal tubercles barely marked; eyes large, finely faceted and distinctly projecting from silhouette of head. Punctures on vertex and frons very fine, inconspicuous; setae short and sparse, slightly suberect, additionally posterior portion of each temple with tuft of thick and long bristles. Antennae slender, AnL 1.20 mm; all antennomeres except III elongate, III slightly transverse; antennomeres VII–XI forming indistinctly delimited club, antennomere XI shorter than IX and X combined, slightly more than 2.5 times as long as broad, weakly flattened.

Pronotum ( Fig. 9 ) in dorsal view broadest near posterior third and strongly narrowing anteriorly and posteriorly, PL 0.36 mm, PW 0.48 mm; area lateroposterior to each anterior corner strongly and abruptly impressed, impression demarcated mesally by longitudinal dorsal ridge; base with long and narrow but shallow transverse groove. Punctures and setae on pronotal disc as fine as those on frons and vertex; sides with thick bristles.

Elytra suboval, broadest distinctly in front of middle, EL 1.00 mm, EW 0.53 mm, EI 1.90; apices separately rounded. Punctures on elytral disc inconspicuous; setae moderately long, very sparse and suberect.

Legs moderately long and slender; protrochanter with slightly projecting and pointed distoventral corner.

Aedeagus ( Figs 17–18 , 25–26 ) stout, AeL 0.33 mm, in ventral view drop-shaped with lateral margins gradually convergent toward apex; endophallus with three large sclerites ( Fig. 49 ), of which the lateral pair is long and weakly recurved and median sclerite is short, broad and rounded at apex; parameres not broadened in subapical region.

Female. Externally differs from male in unmodified protrochanter; BL 1.75 mm; HL 0.40 mm, HW 0.31 mm, AnL 1.08 mm; PL 0.35 mm, PW 0.48 mm; EL 1.00 mm, EW 0.78 mm, EI 1.29.

Distribution. Central Panama, Coclé Province, Olá District; and central-eastern Panama, Panamá Province, Blue Mountains (Cerro Azul).

Etymology. The name plaumannioloides refers to the genus Plaumanniola , which has a very similar aedeagus to that of Rhomboconnus .

Remarks. Euconnus plaumannioloides belongs to a group of small (i.e., with BL distinctly below 2 mm) and sparsely setose Rhomboconnus . It is unique among all members of this subgenus in its anterolaterally impressed pronotum with a pair of ridges extending posterolaterally from anterior corners. It can also be distinguished from all remaining species on the basis of its head, which is weakly narrowing posteriorly and distinctly longer than the pronotum (measurements useful in identifying species are compiled in Table 1); and the pronotum about 1.5 times as broad as the head.

Holotype: Panama (Chiriquí Province): ♂, two labels: " PANAMA, Forest Fortuna / 28/07/2014 / 8,750°N, 82,299°W / litter layer, leg. Tim Struyve" [white, printed], " EUCONNUS / ( RHOMBOCONNUS ) / timstruyvei m. / P. Jałoszyński, '17 / HOLOTYPUS " [red, printed] ( MNHW). Paratype: ♀, same data as for holotype ( TSCB).

Diagnosis. BL ~ 2.5 mm; head, pronotum and elytra with long, moderately dense and suberect to erect setae; tempora strongly narrowing posteriorly; pronotum broadest at base; pronotal base with transverse groove; parameres not broadened in subapical region.

Description. Body of male ( Fig. 2 ) strongly convex, relatively stout, with moderately long appendages, BL 2.50 mm; cuticle glossy, uniformly dark brown, vestiture distinctly lighter than cuticle.

Head ( Fig. 10 ) strongly narrowing posteriorly, broadest at eyes, HL 0.55 mm, HW 0.41 mm; vertex and frons confluent, evenly and weakly convex except frons in front of eyes which steeply declines anteriorly, posterior margin of vertex slightly projecting posteriorly as rounded lobe about as broad as 1/4 of HW; tempora nearly straight in anterior 4/5 and rapidly bent posteromesally in posterior 1/5; supraantennal tubercles barely marked; eyes large, finely faceted and weakly projecting from silhouette of head. Punctures on vertex and frons very fine and inconspicuous; setae long and relatively dense, suberect, additionally posterior margin of vertex and tempora posteriorly with dense row of short bristles. Antennae very long and slender, gradually thickened and slightly flattened distally, AnL 1.53 mm; all antennomeres except III strongly elongate, III slightly transverse; antennomere XI shorter than IX and X combined, ~3.5 times as long as broad.

Pronotum ( Fig. 10 ) in dorsal view broadest at base and strongly narrowing anteriorly, PL 0.55 mm, PW 0.66 mm; base with long and narrow but shallow transverse groove. Punctures and setae on pronotal disc similar to those on frons and vertex; sides with thick bristles directed posterodorsally and dorsally.

Elytra suboval and very broad in relation to pronotum, broadest distinctly in front of middle, EL 1.40 mm, EW 1.18 mm, EI 1.19; apices separately rounded. Punctures on elytral disc more distinct than those on head and pronotum but superficial, small and sparse; setae long, dense and erect.

Legs moderately long and slender; protrochanter unmodified.

Aedeagus ( Figs 19–20 , 27–28 ) stout, AeL 0.50 mm, in ventral view drop-shaped with lateral margins gradually convergent toward apex; endophallus with three long, slender and nearly straight sclerites and one short lateral sclerite ( Fig. 50 ); parameres not broadened in subapical region.

Female. Externally indistinguishable from male; BL 2.53 mm; HL 0.55 mm, HW 0.45 mm, AnL 1.63 mm; PL 0.55 mm, PW 0.68 mm; EL 1.43 mm, EW 0.10 mm, EI 1.30.

Distribution. Western Panama, Chiriquí Province.

Etymology. Euconnus timstruyvei is dedicated to Tim Struyve, who collected all specimens used in this study.

Remarks. Euconnus timstruyvei is the only Rhomboconnus with densely setose dorsum of head, pronotum and elytra. Euconnus silvafortunensis also has setae distributed on the head, pronotum and elytra, but they are sparser (especially those on elytra) than in E. timstruyvei , and the shape of pronotum is clearly different, with the broadest place located in posterior third. The head (but not pronotum and elytra) is densely setose in E. rhombocartianus and E. rhombomiramaranus , and the pronotum and elytra (but not the head) are densely setose in E. perplexus . Euconnus timstruyvei is also the largest known Rhomboconnus , and no other species in this subgenus has the five distal antennomeres so strongly elongate. This species and E. perplexus share a similar shape of the pronotum, which is broadest at base and strongly narrowing anteriorly; the latter species, however, has a strikingly large, asetose and convex head and much less elongate antennae; and its pronotum lacks any antebasal structures, whereas that of E. timstruyvei has a narrow, distinct transverse groove.

Figures

FIGURES 1 – 8. Dorsal habitus of Rhomboconnus species, males. Euconnus plaumannioloides sp. n. (1); E. timstruyvei sp. n. (2); E. silvafortunensis sp. n. (3); E. rhombopanamensis sp. n. (4); E. rhombocartianus sp. n. (5); E. meteti sp. n. (6); E. rhombomiramaranus sp. n. (7); E. rhomboimitator sp. n. (8).

FIGURES 9 – 16. Head and pronotum of Rhomboconnus species, males, in strictly dorsal view. Euconnus plaumannioloides sp. n. (9); E. timstruyvei sp. n. (10); E. silvafortunensis sp. n. (11); E. rhombopanamensis sp. n. (12); E. rhombocartianus sp. n. (13); E. meteti sp. n. (14); E. rhombomiramaranus sp. n. (15); E. rhomboimitator sp. n. (16).

FIGURES 17 – 24. Aedeagus of Rhomboconnus species in ventral (17, 19, 21, 23) and lateral (18, 20, 22, 24) views. Euconnus plaumannioloides sp. n. (17 – 18); E. timstruyvei sp. n. (19 – 20); E. silvafortunensis sp. n. (21 – 22); E. rhombopanamensis sp. n. (23 – 24).

FIGURES 25 – 32. Aedeagus of Rhomboconnus species in ventral (25, 27, 29, 31) and lateral (26, 28, 30, 32) views. Euconnus plaumannioloides sp. n. (25 – 26); E. timstruyvei sp. n. (27 – 28); E. silvafortunensis sp. n. (29 – 30); E. rhombopanamensis sp. n. (31 – 32).

FIGURES 49 – 56. Endophallic sclerites of Rhomboconnus species in ventral view (not to the same scale). Euconnus plaumannioloides sp. n. (49); E. timstruyvei sp. n. (50); E. silvafortunensis sp. n. (51); E. rhombopanamensis sp. n. (52); E. rhombocartianus sp. n. (53); E. meteti sp. n. (54); E. rhombomiramaranus sp. n. (55); E. rhomboimitator sp. n. (56).