Pseudochroaptomus, Chani-Posse & Ramírez-Salamanca & Gualdrón-Díaz, 2024

Chani-Posse, Mariana Raquel, Ramírez-Salamanca, José Manuel & Gualdrón-Díaz, Juliette Cristina, 2024, Pseudochroaptomus ecuadoriensis-a new genus and species of Philonthina and its systematic placement (Coleoptera: Staphylinidae: Staphylininae), Zootaxa 5448 (1), pp. 117-127 : 119-123

Genus Pseudochroaptomus gen. n.

( Figs. 1–9 )

Type species. Pseudochroaptomus ecuadoriensis , here designated.

Etymology. The name of the genus is a combination of the genus name Chroaptomus and the prefix “pseudo” derived from the Greek “pseudes”, meaning “false” or “imitation”. The name is masculine.

Diagnosis. The following combination of characters makes Pseudochroaptomus unique among other genera of Philonthina : antennal insertions in deep fossae, equidistant from both the eye and the anterior margin of the frontoclypeus, the area between them with a rather uniform and smooth microsculpture (i.e., wave-like), lacking distinct grooves, and/or fovea, with a feebly longitudinal impression at most; labrum slightly developed and completely sclerotized; anterior margin of frontoclypeus rather straight; gular sutures joined posteriorly just before the neck. Additionally, its head shape is elongate and parallel-sided for most of its length, slightly narrowed just before the neck into distinctly obtuse hind angles.

Recognition. The habitus colour pattern and general body shape strongly remind of Chroaptomus species. The two genera also share the enlarged and flattened second segment of the palpomere and the thin rod-like paramere. However, in Chroaptomus , the area between the antennal insertions is modified, with a distinct microsculpture (i.e., coriaceous or mesh-like), and grooves and/or fovea slightly to deeply developed in both sexes. The labrum is well developed and partially membranous in males, and the anterior margin of the frontoclypeus is emarginated to subtruncate (not straight), with the gular sutures joined posteriorly shortly before the neck. Additionally, Pseudochroaptomus lacks the sexual dimorphism of the labrum and frontoclypeus present in Chroaptomus , which are unique to the latter. It should also be noticed that all Chroaptomus species currently known bear a paramere no longer than one third the length of the median lobe, in contrast to Pseudochroaptomus , where it is two thirds the length of the median lobe.

Description. Length 8.23–10.17 mm. Body elongate, more or less parallel sided, moderately widening toward elytra and tapering toward sixth visible abdominal segment, scarcely punctate ( Fig. 1 ). Colouration: Head and thorax of dark metallic blue scutellum of bright black, elytra of metallic red and abdomen of bright piceous-black; antennae, palpi and legs piceous to piceous-black. Head and thorax dark metallic blue; elytra metallic red to pink; abdomen strongly iridescent, piceous-black; antennae, palpi and legs piceous to piceous-black.

Head of subrectangular shape, hind angles slightly developed ( Fig. 1 ); slightly to moderately longer than wide, moderately narrower than pronotum at widest point; infraorbital ridge present, slightly extending beyond postgenal ridge; postgenal and ventral basal ridges present, well developed; postmandibular ridge present, strongly developed; epicranium with one pair of long interocular punctures separated from medial margin of eyes by distance about equal to diameter of puncture; dorsal and ventral surface of head with sparse and fine punctation. Eyes moderately convex and large, as long as temples seen from above. Tempora with three to four postocular punctures arranged in a line at each side. Gular sutures joined posteriorly just before neck, at one third of length from anterior margin of submentum to base of head. Eyes moderately convex, as long as temples seen from above ( Fig. 1 ). Antennae inserted in deep fossae, equidistant from both the eye and the anterior margin of the frontoclypeus, slightly posterior to a line drawn between anterior margin of eyes and separated from each other by distinctly more than 2.0 x the distance to eye, first antennomere about one third of head length and distinctly shorter than antennomeres second and third combined, third antennomere distinctly longer than second, first three antennomeres with rather scarce long setae, pubescence on antennomeres 4–11, last (eleventh) antennomere narrowed distad ( Fig. 1 ). Maxillary palpus with second palpomere strongly curved and dilated toward apex, about as long as third palpomere, last (fourth) palpomere fusiform, longer than third and not distinctly narrower ( Fig. 2 ). Labrum subtriangular, distinctly emarginate and completely sclerotized with numerous and long macrosetae at apical margin ( Fig. 2 ). Mentum with anterior margin slightly emarginate and about as long as submentum. Labial palpus moderately long, second palpomere about twice as long as first, third fusiform and longer than second.

Thorax: Pronotum slightly narrowed anteriad, distinctly longer than wide; front margin subtruncate, hind margin broadly arcuate, anterior angles obtuse and posterior angles rounded ( Fig. 1 ); lateral margins slightly sinuate posteriorly in front of hind margin; lateral puncture of pronotum bearing long macroseta separated from superior line of pronotal hypomeron by a distance as large as diameter of puncture; disc with dorsal rows of punctures sub-parallel to each other. Prosternum glabrous, without distinct mid-longitudinal carina; basisternum shorter than furcasternum, with a rudimentary transverse carina. Scutellum large, triangular, and punctuate.

Legs: Profemora subcylindrical in shape, with scarce setae; protibiae setose, with 1–2 medio-apical spines; protarsi with first four protarsomeres subequal in length, simple in both sexes, not dilated, with ventral face bearing only marginal striate setae; meso- and metatibiae distinctly spinose. Elytra at sides longer than pronotum at midline ( Fig. 1 ); punctation moderately coarse. Abdomen: Tergum 1 with paired prototergal glands manifested by invaginated capsules with small openings. Terga 3–5 with both anterior and posterior basal transverse carinae complete and straight. Hind margin of tergum 8 (sixth visible) arcuate in both sexes. Male sexual characters: Sternum 8 emarginate medio-apically ( Fig. 4 ). Genital segment with lateral tergal sclerites 9 (styli) elongate and subcylindrical ( Fig. 3 ); tergum 10 subtruncate at apex with several apical setae and two subapical setae ( Fig. 5 ); sternum 9 with basal portion moderately asymmetrical, distinctly shorter than distal portion and moderately emarginate apically ( Fig. 6 ). Aedeagus with parameres fused as one long, rod-like sclerite, without sensory peg setae, not reaching apex of median lobe; median lobe elongate, with apical part narrowed into distinctly acute apex ( Figs. 3 , 7, 8 ). Female sexual characters: Sternum 8 with hind margin straight; tergum 10 similar to that of male; second gonocoxites each with a long macroseta basally, with minute stylus bearing one long macroseta and one distinctly short and fine seta.

Immature stages and bionomics. Unknown.

Distribution. Pseudochroaptomus is currently only known to inhabit a premontane rainforest at an altitude of 2150 meters in Cosanga, Napo, Ecuador.

Figures

FIGURE 1. Habitus of Pseudochroaptomus ecuadoriensis, male holotype (A) and female paratype (B) [FMNH ©]. Scale bar = 2.5 mm.

FIGURES 2–3. Pseudochroaptomus ecuadoriensis (male paratype) [FMNH ©]: (2) maxillary palpi, labrum and frontoclypeus in dorsal view; (3) tergum 10 and lateral tergal sclerites in dorsal view, aedeagus in lateral view. Scale bar = 0.5 mm.

FIGURES 4–8. Pseudochroaptomus ecuadoriensis, male genitalia [FMNH ©]: (4) male sternum 8; (5) male tergum 10; (6) sternum 9; (7) aedeagus in dorsal view; (8) aedeagus in lateral view (8). Scale bar = 1 mm.

FIGURE 9. A, B, two most parsimonious trees recovered by maximum parsimony analysis, with exclusive (black circles) and non-exclusive (white circles) synapomorphies mapped; C, consensus tree from MP; D, fifty percent majority rule consensus tree resolved by Bayesian inference.All Bremer support values (BS) and posterior probabilities (PP) are shown and indicated in bold for their respective nodes. Values equal or greater than 2 (BS) and/or 0.80 (PP) are considered here as well supported.