Stereocephalus ikiamensis, Żyła & Bieringer, 2025

Żyła, Dagmara & Bieringer, Leander, 2025, A new species of the genus Stereocephalus Lynch, 1884 (Staphylinidae: Paederinae) from the Ecuadorian Amazon, Zootaxa 5646 (4), pp. 593-599 : 595-597

Stereocephalus ikiamensis sp. nov.

urn:lsid:zoobank.org:act:4174E78F-AEA5-41C9-9488-B9349CCA12AF

( Fig. 2A–E )

Type material: Holotype ♂, QCAZ, labelled [all printed]: “DZL-ECU22-03c; ECUADOR Napo, San Juan de Muyuna, research fields of Ikiam Universidad Regional Amazónica, forest buffer for the protected area, next to river Tena , next to path, S0.94985 W77.86514, 610 MASL; leaf litters, winkler, 96% EtOH; 06 vii 2022, leg. K. Bonilla, J. Diaz, C. Guzman, L. Karpiński, K. Koszela, D. Żyła // HOLOTYPE | Stereocephalus ikiamensis Żyła & Bieringer, 2025 [red label]

Etymology: The species epithet is after Universidad Regional Amazónica IKIAM, Ecuador, where the specimen was collected in recognition of its contributions to research and biodiversity conservation. It is a Latinized adjective.

Diagnosis: The species can be easily distinguished by the dorsal plate of the aedeagus, which has a bifurcate apical half where each branch is hook-like with the apex bent outward. Additionally, it differs from S. myrigeus and S. ruhus by the presence of two impunctate, polished, medial spots on the head disc (absent in the other two species), from S. agostii by the ventral sclerite of the aedeagus gradually curved towards the apex (abruptly bent upward subapically in S. agostii ), and from S. seriatipennis by the ventral sclerite of the aedeagus with the apex blunt (slender and pointed in S. seriatipennis ). In the structure of the aedeagus, S. ikiamensis sp. nov. most resembles S. rinnanus , but clearly differs by the lack of median emargination at the apex of the ventral sclerite (a shallow emargination present in S. rinnanus ) and by the dorsal plate divided into two branches with a hook-like apex bent outwards (branches slightly bent inwards, without a hook-like apex in S. rinnanus ).

Description: Body length 8.17 mm; fore body length 5.0 mm. Colouration reddish brown, head darker and appendages light brown to yellowish ( Fig. 2A ).

Head: Head slightly wider (1.71 mm) than long (1.53 mm). Epicranium and vertex with umbilicate punctuation, space between punctures (interstices) much smaller than diameter of punctures, punctures close together, punctures denser towards centre, absent in middle, forming two impunctate central spots. Eyes three times shorter than head, half of temple length. Antenna (2.81 mm) shorter than head and pronotum combined; antennomere 1, as long as antennomeres 2 and 3 combined, antennomere 3 longer than 2, antennomeres 4–7 as wide as long, antennomeres 8–10 wider than long, antennomere 11 more than twice as long as wide, narrowing at apex; tomentose pubescence starting from antennomere 4. Labrum transverse, with V-shaped median emargination reaching half of labrum length, anterior margin with row of setae. Mandibles broad and dentate, both with two teeth; right mandible with apical tooth largest, left mandible with both teeth of similar size. Maxillary palpus with palpomere 1 triangular shaped, narrow at base and widening towards apex, with one seta in middle and three setae at apex; palpomere 2 elongate, much shorter than others; palpomere 3 triangular, but much larger than palpomere 1, widening towards apex, with scattered setation; palpomere 4 only slightly narrower than apex of palpomere 3, but much shorter. Ligula (partially fused glossae) with two translucent ventrolateral lobes. Labial palpus with palpomere 1 much shorter than 2, broadening towards apex, palpomere 2 elongated, broadening towards tip, slightly bent; palpomere 3 small and needle-like, narrowing towards tip. Posterior margin of head in ventral view deeply concave. Head ventrally with umbilicate punctuation, space between punctures less than punctures diameter. Neck wide (0.94 mm), more than half of head width.

Thorax: Pronotum widest in anterior 1/4, almost as long (1.52 mm) as wide (1.57 mm); anterior margin rounded, forming approximately 110° angle with lateral margin; lateral margins straight, narrowing towards posterior margin; rounder posteriorly, posterior margin straight; disc shiny, with umbilicate punctuation, forming roughly two rows on both sides of impunctate middle area, unorganised punctures laterally, no microsculpture between punctures. Prosternum surface with superior marginal line deflexed; pronotosternal suture present, well developed near coxal cavity and absent anteriorly; basisternum without transversal carina; longitudinal carina apically transforming to elevated surface, ending before anterior margin; furcasternum well separated from hypomeron, triangular, with sharp longitudinal carina in middle, as long as tip of postcoxal process. Hypomeron with postcoxal process with additional carina and scattered punctures. Central sclerotisation of prepectus on mesosternal surface trapezoidal, with two depressions near anterior margin. Two secondary ridges extending from narrowed part of central sclerotisation of prepectus and fused with preepisternal ridge, forming two enclosed areas with wrinkled microsculpture and several punctures. Preepisternal lateral areas with additional ridge and several punctures. Mesobasisternum as wide depression, pair of setae in posterior third, and scattered punctures. Ridges aligned with anapleural connection well developed. Mesosternum clearly separated from metasternum. Ridge below coxal rest on metasternum well developed. Scutellum with two emarginate transversal ridges, posterior ridge U-shaped, pointed towards base; impunctate, except for apex with scattered micropunctuation. Elytra rectangular, longer (1.89 mm) than wide (1.76 mm); epipleural ridge present; apical margin only slightly emarginate, with row of setae on apical margin; apical angle rounded; dorsal surface with umbilicate punctures forming distinctive rows; no microsculpture between punctures.

Legs: Protrochantin tear-shaped; 1/3 procoxa length; procoxa longer than wide; profemur widest in middle, narrowing towards apex, with “cleaning” comb on inner margin; protibia widening towards apex, with four fullydeveloped combs of setae and three associated macrosetae, apex with spine-like ctenidium on ventral side; protarsi dilated, with long, adhesive setae underneath and dense, yellow pubescence on ventral side, protarsomere 1–4 progressively smaller in length and width, protarsomere 5 longest, as long as protarsomeres 2–4 combined. Mesotibia with spine-like ctenidium on inner side, with two spurs ventrally; mesotarsomere 1 as long as 2 and 3 combined, mesotarsomere 2–4 similar length, mesotarsomere 5 slightly shorter and more slender than mesotarsomere 1. Metacoxa divided into glabrous distal part and setose apical part, divided by deep suture, metatrochanter rounded, metatibia with ctenidium on inner side and short row of setae on outer side, two spurs ventrally; metatarsomere 1 as long as 2 and 3 together with dense pubescence, metatarsomere 2– 4 similar length, metatarsomere 5 slightly shorter than 1, without pubescence.

Abdomen: Surface with micropunctures arranged randomly, finger-print like microsculpture. Segments III–VI with straight posterior margin. Segment III–VII gradually increasing in length.Tergites III–VI impressed transversely at base. Sternite III with central longitudinal keel, reaching half of sternite length. Posterior margin of tergite VII slightly convex, without emargination. Posterior margin of sternite VII with shallow emargination. Posterior margin of tergite VIII convex, narrowing toward apex ( Fig. 2B ). Posterior margin of sternite VIII with median V-shaped emargination and rounded lateral angles; emargination reaching 1/4 of sternite length ( Fig. 2C ). Tergite IX, posterior margin convex, mid-dorsal base fused medially. Tergite X trianguloid, with long and strong setae in posterior half.

Aedeagus: Median lobe of aedeagus, in parameral view, gradually and slightly tapered towards apex, with apex slightly widened; apex convex, with sides bent inwards forming tube-like structure ( Fig. 2D ); dorsal (antiparameral) plate with bifurcate apical half ( Fig. 2D ); each branch slender and hook-like with apex bent outwards ( Fig. 2E ). Internal sac with pair of anteriorly directed short struts.

Figures

FIGURE 2. Stereocephalus ikiamensis sp. nov. holotype ♂. A. habitus in dorsal view. B. Tergite VIII in dorsal view. C. Sternite VIII in ventral view. D. Aedeagus in antiparameral view. E. Aedeagus in lateral view.