Gibbidessus drikdrikensis, Hendrich & Watts & Balke, 2020

Hendrich, Lars, Watts, Chris H. S. & Balke, Michael, 2020, The " minute diving beetles " of southern Australia - taxonomic revision of Gibbidessus Watts, 1978, with description of six new species (Coleoptera, Dytiscidae, Bidessini), ZooKeys 975, pp. 11-49 : 11

Gibbidessus drikdrikensis sp. nov. Figs 5 , 17 , 22

Type locality.

Australia, Victoria, Drik Drik, old farm dam [37°59'27S, 141°17'18E].

Type material.

Holotype: Male, "1 km S, Drik Drik Vic. 24/9/98 C. Watts", “Photographed”, " SAMA Database No 25-004000", "Holotype Gibbidessus drikdrikensis sp.nov. Hendrich, Watts & Balke des. 2020" [red printed label] (SAMA). Paratypes (6 exs.): 6 specimens with same data as holotype. Two specimens with "DNA voucher b" and "DNA voucher c" and one with a yellow prointed label “photographed” (CLH, SAMA). All paratypes are provided with printed red paratype labels.

Diagnosis.

Medium-sized species which externally is characterised by a wide rounded body, shiny non-microreticulate dorsal surface, vague testaceous markings on elytra, and without slight habitus disruption between pronotum and elytron. Dorsoventrally rather domed. Cervical line present (Fig. 5 ).

Measurements.

Holotype: TL = 1.7 mm, TL-H = 1.5 mm, MW = 0.98 mm. Paratypes: TL = 1.6-1.7 mm, TL-H = 1.4-1.5 mm, MW = 0.86-0.98 mm.

Head: Dark brown, around eyes almost black. Cervical line present. Strongly and coarsely punctate, rather shiny, microsculpture almost absent. Punctures weakly anteriorly and strongly posteriorly between eyes. Antennae relatively short, stout. Antennomeres 1 and 2 ferruginous, 3-11 darkened anteriorly.

Pronotum: Ferruginous, anterior and posterior margins darker. Disc of pronotum somewhat darkened, broadest at posterior corners. Punctation very weak, almost evenly distributed, shiny and microsculpture absent. Sides of pronotum margined and almost evenly rounded. Angle between pronotum and elytra not pronounced, basal pronotal plicae present. Striae well defined, almost 1/2 length of pronotum, strongly incurved.

Elytra: Ferruginous, with vague areas darkened (Fig. 5 ). Coarsely and densely punctate, shiny, microsculpture absent. Striae strongly impressed, same length as basal pronotal striae but slightly straighter.

Ventral side: Ferruginous. Prothorax and abdomen paler than other parts. Metacoxae and metaventrite covered with numerous larger punctures, surface shiny, without microreticulation. Abdominal ventrites with dense and finer punctures, shiny, microreticulation absent. Metacoxal lines almost straight, anteriorly slightly divergent. Epipleuron testaceous, with few coarse punctures, shiny, lacking microsculpture. Legs ferruginous meta-/mesotarsi set in black.

Male. Dorsal surface with coarse punctures but otherwise with shiny surface (Fig. 5 ). Median lobe of aedeagus as in Fig. 17A, B . Shape of median lobe fairly uniform, evenly bent in lateral view, apex straight and pointed at tip in ventral view. Parameres bi-segmented, broad and with few setae at apex (Fig. 17C, D ).

Affinities.

This species is very similar to G. chipi but readily separated by its larger size and the form of the median lobe and parameres (Figs 15 , 17 ).

Etymology.

The species is named after the type locality. The specific epithet is a substantive in the genitive case.

Distribution.

Only known from the type locality Drik Drik in south-western Victoria (Fig. 22 ).

Habitat.

The few specimens were collected in shallow water at the edge of a large, exposed but shallow farm dam, overgrown with grasses and sedges. The species is syntopic with G. chipi .

Figures

Figures 5 - 7. Habitus of 5 Gibbidessus drikdrikensis sp. nov. 6 G. kangarooensis sp. nov. 7 G. pederzanii sp. nov. Scale bar: 1.0 mm.

Figures 16, 17. 16 Gibbidessus davidi sp. nov. 17 G. drikdrikensis sp. nov. A median lobe in ventral view B median lobe in lateral view, left side C left paramere in lateral view, D right paramere in lateral view. Scale bar: 0.2 mm.

Figures 22, 23. Distribution of 22 Gibbidessus chipi (black dots), G. drikdrikensis sp. nov. (yellow square), G. kangarooensis sp. nov. (red square) 23 G. atomus sp. nov. (red square), G. davidi sp. nov. (yellow square).

Figures 14, 15. 14 Gibbidessus atomus sp. nov. 15 G. chipi A median lobe in ventral view B median lobe in lateral view, left side C left paramere in lateral view. Scale bar: 0.2 mm.