Gymnochthebius truncatus Perkins 2005, new species
Creators: name: Perkins, Philip D.
Publisher: name: Zenodo
Year: 2005
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Hydraenidae
Gymnochthebius
Gymnochthebius truncatus

description: <i>Gymnochthebius truncatus</i> new species (Figures 7, 8, 74) <b>Type Material.</b> Holotype (male): <b>Australia: Queensland:</b> Cape York, Archer River, Archer Bend, moderately large shallow billabong/pool in otherwise dry river bed; unvegetated with thick layer of dead leaves etc., 13° 28' S, 142° 12' E, 28 September 1983, C. Watts. Deposited in the SAMA. <b>Paratypes (23): Australia: Northern Territory:</b> Kakadu NP, Malapanbanjo Ck, c. 8 km S of Arnhem Hwy on Pine Creek Rd., 12° 16' S, 132° 40' E, M. B. Malipatil (1 MAGD); Nourlangie Creek, 8 km. E of Mt. Cahill, mud at edge of waterhole, 12° 52' S, 132° 47' E, 27 October 1972, E. B. Britton (15 ANIC); <b>Queensland:</b> 10 km WNW of Rokeby (Mango Lagoon), lagoon with rocks at edge, 13° 38' S, 142° 35' E, 27 October 1992, P. Zborowski, T. Weir (2 ANIC); Cape York, Archer River, Archer Bend, moderately large shallow billabong/pool in otherwise dry river bed; unvegetated with thick layer of dead leaves etc., 13° 28' S, 142° 12' E, 28 September 1983, C. Watts (4 SAMA); Ling Creek, watersweep, 12° 19' S, 142° 10' E, 14 August 1993, P. Zborowski &amp; J. Balderson (1 ANIC). Representative specimens to be deposited in MCZ and NPC. <b>Differential Diagnosis.</b> Recognized by the truncate body form, the shining dorsum, the shallowly striate­impressed elytral series, the large, shining, subrhomboidal metasternal glabrous area, and the abdominal ventrites 1–2 and basally 3 with hydrofuge pubescence. The dorsal sculpture is somewhat similar to that of <i>G. angulonotus</i>, but the two species differ in body proportions and size (Figs. 5, 7). The male genitalia have two barbs on each lobe, as does <i>G. levis</i>, but the two species differ in most other genitalic characters and are so different externally as to defy comparison. <b>Description.</b> Size (length/width, mm) holotype: body (length to elytral apices) 1.49/ 0.71; head 0.30/0.44; pronotum 0.33/0.59; elytra 0.94/0.71. Form moderately ovate, moderately convex. Color dark brown, legs lighter, dorsal reliefs moderately shining. Frons very finely sparsely punctate, very sparsely pubescent; interocular foveae deep; interocular tuberculi distinct; basal midlongitudinal fovea confluent with interocular foveae. Frontoclypeal suture deeply impressed, bisinuate. Clypeus midlength 0.5 apical width, very sparsely punctate; pubescence sparse on disc, denser laterally. Labroclypeal suture straight in dorsal view, evenly arcuate in anterior view. Labrum width twice length; anterior margin arcuate, with very low upturned apicomedian tooth. Pronotum lateral hyaline border well developed, origin at base of lateral depression, arcuate to posterior angles, very narrow around posterior margin; anterior margin of pronotum arcuate in midregion; each lateral depression with posterior in form of right angle, lateral margin distinctly setose; lateral fossulae deep, lacking microsculpture; pronotal disc moderately convex, extremely finely sparsely punctate, each puncture with a recumbent seta; median groove moderately deep, narrow, extending nearly to margins, tapering at ends; anterior foveae shallow, sides gradually sloping; posterior foveae oblique, shallow, linear impressions nearly 1/2 as long as and as wide as median groove, sides gradually sloping; posterolateral angles without impressions. Elytra convex on disc, with six rows of slightly elongate, closely spaced punctures in shallow striae between suture and humeri; each puncture with a decumbent seta that overlaps base of following seta; intervals slightly rounded, width 2–3x that of punctures; summit of declivity at midlength; explanate margin narrow, with fringe of long setae. Metasternal glabrous area length less than width (as 14:20), subrhomboidal, anteriorly nearly attaining intercoxal process, shining, convex. Abdominal ventrites 1–2 and basally 3 with hydrofuge pubescence. Aedeagus (Fig. 8): Length of main­piece 0.25 mm, length to tip of parameres 0.26 mm; lobes relatively long and slender, each with two barbs; dorsal notch U­shaped, widest apically, slightly deeper than ventral notch; apical paramere seta elongate, much longer than other setae. Females have the elytral explanate margin similar to that of males; the anterior margin of the labrum is arcuate. <b>Etymology.</b> Named in reference to the body form. <b>Distribution.</b> Currently known from northern Queensland and northern Northern Territory (Fig. 74).
description: Published as part of <i>Perkins, Philip D., 2005, A revision of the water beetle genus Gymnochthebius Orchymont (Coleoptera: Hydraenidae) for Australia and Papua New Guinea, pp. 1-161 in Zootaxa 1024 (1)</i> on pages 1-161, DOI: 10.11646/zootaxa.1024.1.1, http://zenodo.org/record/5049567