Thambus woodruffi Muona 2022, new species

Thambus woodruffi Muona, new species Figures 6, 7. Etymology. Named in honor of the late Robert E. Woodruff, whose many interests included fossil resins and especially the Dominican amber fauna. Holotype. Embedded in flat, rectangular Dominican resin piece with broadly rounder corners, 17 mm × 11 mm, female. The same piece includes an unidentified throscid beetle as well as other insects (Fig. 7). Diagnosis. The length/width ratio of all other Thambus species is 2.4–2.8, in this species it is about 2.1. Description. Elateroidea synapomorphy: pro-mesocoxal clicking mechanism present. Eucnemidae synapomorphies: pedicel attached subapically to scape, labrum hidden, elytral striae apically grooved with excretory punctures (Fig. 6). Eucnemidae other characters: abdominal ventrites connate (Fig. 7). Macraulacinae synapomorphy: hypomera with basally open lateral antennal grooves (Fig. 7). Macraulacini other characters: hypomera without excretory pits, metasternum without tarsal grooves. Length 3.0 mm. Form very wide, ratio L/W about 2.1 (Fig. 6). Pronotum wider than long and wider than elytra with slightly expanded, acute non-carinate hind angles, evenly and densely punctate (Fig. 6). Scutellum transverse, widely triangular, apex cut off, elytra with sharp, complete sutural striae with deep apical excretory groove continuing around to lateralmost striae, densely and finely punctate, other striae faint but present (Fig. 6). Head rounded, densely punctate, eyes large, flat, frons wide, without carinae, frontoclypeus apically about 1.3 times as wide as between antennal sockets, mandibles short, bifid (Fig. 7). Antennae fairly short, reaching slightly past the hind angles, scape as long as pedicel plus f1 and f2 combined, f2–f3 feebly serrate, f4–f7 not visible, f9 1.4 times as long as f8, both longer than wide. Hypomeron with sharply defined, basally open lateral antennal grooves, about triangular, sparsely punctate, without excretory pits (Fig. 7). Prosternum wide, moderately densely punctate, prosternal peg long, triangular, acute, deeply marginate, metasternum wide and long, densely punctate, without tarsal grooves, elytral epipleura simple. Metacoxal plates triangular, widest close to midline, angle tightly rounded and there less than times as wide as on sides, densely punctate. Legs long and delicate, meso- and metatarsi shorter than tibiae, meso- and metatarsomere 1 slightly shorter than the others combined, fourth apically narrowly bilobed, excavated, claw simple (Fig. 6, 7). Abdominal ventrites connate, densely and finely punctate (Fig. 7). Remarks. Thambus Bonvouloir is a primarily tropical American genus, with additional species known from Europe (1), China (1), Japan (1) and North America (1). The species are small, have a basally wide pronotum with sides strongly converging craniad. In addition to their shape and small size, Thambus species are characterized by round pit-like areas laterally on the prosternum. This feature varies between species from faint (e.g. T. deyrollei Bonvouloir) to conspicuous (e.g. T. friwaldskyi Bonvouloir). These pits are not visible in the present sample, but the other characters listed place it to Macraulacini and within this tribe the correct placement is clearly Thambus. Family Eucnemidae Eschscholtz, 1829 Subfamily Macraulacinae Fleutiaux, 1922 Tribe Macraulacini Fleutiaux, 1922
Published as part of Muona, Jyrki, 2022, New fossil false click-beetles from the Americas (Coleoptera: Eucnemidae), pp. 1-11 in Insecta Mundi 2022 (912) on pages 6-9, DOI: 10.5281/zenodo.6391857