Syndicus (s. str.) minimus, Jałoszyński, 2023

Jałoszyński, Paweł, 2023, A new species of Syndicus s. str. from Sumatra (Coleoptera, Staphylinidae, Scydmaeninae), Zootaxa 5315 (6), pp. 593-599 : 594-596

Syndicus (s. str.) minimus sp. n.

( Figs 1–8 )

Type material studied. Holotype ( Indonesia: Sumatra): ♁, two labels: “SUMATRA: Aceh # 25a / Mt. Leuser NP, 300- / 500 m, Ketambe, 23 / 30.XI.1989, Löbl / Agosti, Burckhardt” [white, printed], “ SYNDICUS (s. str.) / minimus m. / P. Jałoszyński, ’23 / HOLOTYPUS” [red, printed] ( MHNG) . Paratypes (10 exx.): 1 ♁, 1 ♀, same data as for holotype; 1 ♁, “SUMATRA: W Sum. / Panti, 250 m / 19.XI.1989 / Agosti, Löbl / Burckhardt # 23” [white, printed]; 2 ♁♁, “ Sum-06/04: SUMATRA: / West Sumatra Province, / Anai Valley, 6km S of / Padangpanjang, 0°28’38’’S, / 100°21’14’’E, 500m / (primary forest); 1.VI.2006, / leg. A. Schulz. Sum-06/04 ” [white, printed]; 1 ♁, “ Sum-06/22: SUMATRA: / North Sumatra Province, / Sipirok, Dolok Sipirok / National Park, near hot / springs, ca 30 km N of / Padangpanjang, / 1°33’55’’N, 99°17’03’’E, / 1000m (disturbed hill / forest); 16.VI.2006, / leg. P. / Schwendinger. Sum-06/22 ” [white, printed]; 1 ♁, 1 ♀, “ Sum-06/18: SUMATRA: / West Sumatra Province, / Rimbo Panti Nature / Reserve, ca. 30km N of / Lubuksikaping, 0°20’46’’N, / 100°04’09’’E, 300–400m / (primary forest); / 11/ 13.VI.2006, leg. P. / Schwendinger. Sum-06/18 ” [white, printed]; 1 ♁, 1 ♀, “ Sum-06/20: SUMATRA: / West Sumatra Province, / disturbed primary forest / near road Lubuksikaping - / Bonjol , ca 10km S of / Lubuksikaping , 0°03’16’’N, / 100°12’33’’E, 500m; / 12.VI.2006, leg. P. / Schwendinger. Sum-06/20 ” [white, printed]. Paratypes in cPJ and MHNG .

Diagnosis. Male and female with virtually impunctate frons and vertex; vertex with small and shallow median impression; punctures on pronotal disc fine, inconspicuous; punctures on elytra remarkably large and deep; endophallus in ventral view with large distal and small proximal vesicles, butterfly-shaped central complex and conspicuously long proximal projection; each paramere in lateral view with strongly broadened apex bearing on mesal surface several long and thick setae; spermatheca in axial view oval, lacking subconical projection at insertion of ductus spermathecae, in ‘lateral’ view hat-shaped, strongly convex at middle and abruptly flattened laterally.

Description. Body of male ( Figs 1, 2 ) strongly elongate, strongly convex; pigmentation dark brown, legs and palps distinctly lighter, body covered with brown setae distinctly lighter than cuticle; BL 2.30–2.50 mm.

Head broadest at eyes, HL 0.38–0.40 mm, HW 0.50–0.55 mm; tempora weakly rounded, in dorsal view each ~1.5 times as long as eye, strongly and evenly converging posterad, median region of vertex indistinctly elevated and with small and shallow median impression (variable in shape, in some specimens elongate, in others nearly punctiform, but present in all studied beetles); supraantennal tubercles prominent, their posteromedian margins slightly impressed. Eyes moderately large and weakly convex, finely faceted, each distinctly oval and lacking posterior emargination. Dorsum of head virtually impunctate, glossy; setae thin, sparse, long and suberect, postgenae with several thick bristles directed lateroposteriorly. Antennae slender and indistinctly thickening distally, AnL 1.53–1.70 mm, all antennomeres except 11 elongate (2 and 3 indistinctly so), 10 and 11 together equal to 1.5 × length of 9.

Pronotum less convex than elytra ( Fig. 2 ), elongate, broadest near anterior fourth, PL 0.68–0.75 mm, PW 0.55–0.60 mm. Sides strongly rounded in anterior half, posteriorly weakly sinuate, anterior corners weakly marked, anterior margin strongly arcuate, posterior corners obtuse-angled and blunt, posterior pronotal margin nearly straight. Pronotal disc demarcated from short posterior ‘collar’ by transverse row of two dorsal pairs and two lateral pairs of large, deep and nearly circular pits. Punctures on disc distinct but fine and shallow, unremarkable; setae thicker, longer and denser than those on frons and vertex, sparse and suberect; sides of pronotum with sparse thick bristles.

Elytra together oval, broadest distinctly in front of middle; EL 1.20–1.33 mm, EW 0.83–0.90 mm, EI 1.43–1.52; humeral calli and basal impressions barely marked; elytral apices separately rounded. Punctures on entire surface of elytra remarkably distinct, large and deep, separated by spaces subequal to their diameters; setae similar to those on pronotum but slightly longer.

Hind wings lacking.

Legs slender and long, unmodified; profemoral clava somewhat subtriangular in lateral view, with clearly defined highest site, glandular opening on dorsal region of each femur distinct and situated in subapical region, dorsal longitudinal groove on each femur distinct between glandular opening and distal margin of femur, but becoming indistinct towards femoral base; protibiae straight, mesotibiae indistinctly curved inwards, metatibiae barely discernibly sinuate.

Aedeagus ( Figs 3–6 ) weakly elongate, AeL 0.45 mm; median lobe in ventral view broadest in submedian region, apex broadly subtrapezoidal and truncate; endophallus with darkly sclerotized, symmetrical components: medially situated butterfly-shaped central complex, distally connected with broad tubular structure flanked by elongate, sinuate sclerites; vesicular region of endophallus composed of large distal and small proximal vesicles and with long and slender proximal projection; parameres slender, in lateral view each strongly broadened in apical region and bearing several long and thick apical setae on mesally concave apex.

Female. Externally indistinguishable from male. Spermatheca ( Figs 7, 8 ) in ‘lateral’ view hat-shaped with long sclerotized duct of accessory gland, in axial view slightly oval, longer diameter 0.10 mm. BL 2.25–2.33; HL 0.35–0.38 mm, HW 0.50–0.53 mm, AnL 1.50–1.53 mm; PL 0.68–0.73 mm, PW 0.55–0.58 mm; EL 1.20–1.25 mm, EW 0.80–0.85 mm, EI 1.47–1.50.

Distribution. Indonesia: Sumatra.

Etymology. The adjective minimus refers to the exceptionally small body of adults.

Remarks. The large and deep elytral punctures strongly contrasting with fine punctures of the head and pronotum are unique and allow for easy identification of S. minimus . The aedeagus of S. minimus resembles those of S. echinatus Jałoszyński, 2004 , and S. sculpturatus Jałoszyński, 2004 in the structure of the endophallus. However, the parameral apices of S. minimus are strongly broadened in lateral view, while those in S. echinatus and S. sculpturatus are narrowed. The only species with the parameral apices strongly broadened in lateral view is the Vietnamese S. lamdongianus , and if the key from Jałoszyński (2004) is used, males of S. minimus would be identified as S. lamdongianus . However, these two species differ clearly in external features. Syndicus lamdongianus is clearly larger (BL 2.64–2.99 mm vs. 2.25–2.50 mm in S. minimus ), has lateral margins of pronotum weakly rounded (strongly rounded in S. minimus ), and the elytral punctures fine and shallow. The central complex of the endophallus in S. lamdongianus (for terminology of endophallic structures see Jałoszyński (2011): fig. 4) is rhomboidal in ventral view (butterfly-shaped in S. minimus ), and the broadened parameral apices bearing a large number of minute setae (several long setae in S. minimus ); the spermatheca in the Vietnamese species in ‘lateral’ view is subcylindrical, and not hat-shaped, as that in S. minimus . The shape of the spermatheca of the new species is unique, but females remain unknown for several species, so the external features and the aedeagus are primary diagnostic characters for S. minimus .

The only member of the nominotypical subgenus known so far to inhabit Sumatra was S. paeninsularis klapperichi Franz (redescribed in Jałoszyński (2004)). Syndicus paeninsularis includes three subspecies distributed in Malaysia: Pahang, Sabah ( S. paeninsularis heissianus Jałoszyński, 2004 ); Indonesia: Sumatra, Malaysia: Pahang and Tioman Island ( S. paeninsularis klapperichi ); and in Singapore ( S. paeninsularis paeninsularis L.W. Schaufuss, 1889 ). This is the only species with the clypeus conspicuously modified, anteriorly elevated to form a roof-like structure over the labrum (illustrated in Jałoszyński (2004): fig. 18A–H), while in all remaining species, including S. minimus , the clypeus is unmodified and gradually declining anterad towards the posterior labral margin.

Figures

FIGURES 1‒8. Syndicus (s. str.) minimus sp. n. Dorsal (1) and lateral (2) habitus; aedeagus in ventral (3, 5) and lateral (4, 6) views; spermatheca in ‘lateral’ (7) and axial (8) views.