Trechisibus brevis, Allegro, Gianni & Giachino, Pier Mauro, 2016

Allegro, Gianni & Giachino, Pier Mauro, 2016, Nine new Trechisibus species from Peru and Argentina (Coleoptera: Carabidae: Trechinae), Zootaxa 4193 (1), pp. 49-72 : 65-66

Trechisibus brevis n. sp.

( Figs. 10 a, 10b, 10c, 10d, 19)

Type locality. Argentina, Neuquen, Pen. Quetrihué.

Diagnosis. A Trechisibus species 3.42 mm long, dark brown and shiny; legs, antennae, mouth parts and lateral border of elytra reddish brown. Hind angles of pronotum acute and protruding backwards and outwards. Elytra short oval, obovate, widest behind middle, moderately depressed on disc, with 2 discal setigerous punctures (in addition to the preapical pore) on the 3rd stria, the first at about 1/5 from base and the second just behind middle. T. brevis n. sp. is distinguished from all other Trechisibus species distributed in Patagonia by the body short and obovate ( Fig. 10 a) and by the peculiar morphology of the median lobe of aedeagus, provided with a distinct ventral swelling in lateral view ( Fig. 10 b).

Type Series. HT ♂, Argentina, Neuquen, Pen. Quetrihué, 12.II.1998, legit Riccardo Sciaky (CAl).

Description. Habitus as in Fig. 10 a. Overall length of the HT ♂ (from labrum to apex of elytra) 3.42 mm. Body dark brown, obovate, shiny. Microsculpture markedly impressed on head, very superficial on pronotum and nearly absent on elytra. Legs, mouth parts, antennae and lateral border of elytra reddish brown. Brachypterous.

Head moderately large, eyes small and convex; temples hardly convex and delicately pubescent, as long as eyes. A microsculpture in isodiametric meshes markedly impressed on whole upper surface of head. Clypeus with two apical setae on each side; labrum transverse, 6-setose, distinctly excavate at apex. Frons between eyes convex without depression on vertex. Antennae moderately long, hardly reaching the basal 4th of elytra.

Pronotum convex on disc, transverse (width/length = 1.36), with base as wide as the anterior margin ( Fig. 19 ). Disc almost shiny and microsculpture very superficial but visible on the whole pronotum. Sides rounded for most of their length, shortly sinuate before hind angles; basal margin sinuate at sides. Front angles feebly prominent; hind angles acute and protruding backwards and outwards. Mid longitudinal line distinctly impressed between the submarginal sulci, deepened towards base. A wide basal impression on each side, separated at middle by the wrinkled convexity of the base. Lateral border narrow on whole length; anterior margin unbordered, the posterior bordered only at sides. Two lateral setae on each side, one at hind angles (moved a little forwards from the angle) and one at about 2/3 from base.

Elytra short oval (length/width=1.27), widest behind middle, feebly depressed on disc. Microsculpture in transverse meshes very superficial, nearly absent on disc. Shoulders rounded with humeral angle indistinct. The basal margin interrupted in correspondence with the 5th stria. A short scutellar stria is present, as well as a juxtascutellar pore near base, in correspondence with the 2nd stria. Sides moderately rounded; lateral border narrow in the fore half, posteriorly widened, reddish brown and distinctly contrasting in colour with the darker elytra. Two discal setigerous punctures in small and superficial foveae on the 3rd stria, the 1st at basal 5th of elytra and the 2nd just behind middle; the punctures divert the 3rd stria linearity; preapical pore at about middle of the recurrent striole. Umbilicate series of 4+2+2 punctures, with groups widely spaced from each other. The five inner striae moderately impressed, the others obliterated; the 8th stria deeply impressed in the posterior half. Intervals nearly flat. Elytral apex broad and rounded. The recurrent striola moderately long and arcuate.

Legs slender. Protibiae nearly straight and externally distinctly furrowed. Tarsi pubescent on the upper side. The 1st and 2nd male protarsomeres asymmetrically dilated.

Median lobe of aedeagus slender in lateral view, provided with a distinct ventral swelling and hardly bent downward at apex ( Fig. 10 b); apical blade short and, in dorsal view, widely triangular, blunt at the extreme apex ( Fig. 10 c). Little can be said about the internal armature, as the only known specimen (HT) shows it evaginate; a bundle of sclerotized scales is present ( Figs. 10 b, 10c). Parameres wide and short, almost equally long, each provided with 4 apical setae ( Fig. 10 b).

Etymology. The specific epithet refers to the short oval shape of the body.

Distribution and habitat. At present Trechisibus brevis n. sp. is only recorded from the type locality. The specimens of the type series were collected at about 800 m a.s.l.

Relationships. At the present state of knowledge, the phylogenetic affinities of Trechisibus brevis n. sp. are unclear, but despite the strong differences in the morphology of the aedeagus, this species shares many external morphological features with Trechisibus striatus n. sp., Trechisibus sciakyi n. sp. and Trechisibus longipenis n. sp.

Figures

FIGURE 10. Trechisibus brevis n. sp. HT: habitus (a); median lobe of aedeagus in lateral view (b); median lobe of aedeagus in dorsal view (c).

FIGURES 17 – 21. Pronotum of Trechisibus: striatus n. sp. HT (17); sciakyi n. sp. HT (18); brevis n. sp. HT (19); longipenis n. sp. HT (20); parvulus n. sp. HT (21).