Gibbidessus kangarooensis, 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 kangarooensis sp. nov. Figs 6 , 18 , 22

Type locality.

South Australia, Kangaroo Island, Eleaner River at South Coast [Road] Crossing, edge sample [35°56'S, 137°14'E].

Type material.

Holotype: Male, "Eleaner R. S, Coast rd AWQ [Australian Water Quality] survey 8/11/95 site 3714 [35°56'S, 137°14'E]" "Holotype Gibbidessus kangarooensis sp. nov. Hendrich, Watts & Balke des. 2020" [red printed label] (SAMA).

Diagnosis.

Small species which externally is characterised by a more elongate body, shiny non-microreticulate dorsal surface, and with well pronounced habitus disruption between pronotum and elytron. Dorsoventrally rather flattened. Without cervical line but rather a few punctures instead (Fig. 6 ).

Measurements.

Holotype: TL = 1.55 mm, TL-H = 1.4 mm, MW = 0.88 mm.

Head: Ferruginous, without cervical line but rather a few punctures instead. Evenly and coarsely punctate, shiny, microsculpture absent. Punctures weakly anteriorly and strongly posteriorly between eyes. Antennae missing.

Pronotum: Ferruginous, anterior and posterior margins darker, broadest at middle. Punctation weak anteriorly but quite strong on posterior half and on lateral sides, almost evenly distributed, shiny and microsculpture absent. Sides of pronotum broadly margined and almost evenly rounded. Angle between pronotum and elytra well pronounced, basal pronotal and elytral plicae present. Striae moderately defined, almost 1/2 length of pronotum, strongly incurved.

Elytra: Dark brown with vague basal area ferruginous (Fig. 6 ). Coarsely and densely punctate, shiny, microsculpture absent. Striae weakly impressed, slightly straighter and of same length as basal pronotal striae.

Ventral side: Ferruginous. Prothorax and apex of abdomen paler than other parts. Metacoxae and metaventrite covered with numerous larger punctures, surface shiny, without microreticulation. Abdominal ventrites with finer punctures, shiny, microreticulation absent. Metacoxal lines almost straight, anteriorly slightly divergent. Epipleuron ferruginous, coarsely punctate, shiny, lacking microsculpture. Legs ferruginous with meta-/mesotibia and meta-/mesotarsi somewhat darkened.

Male. Dorsal surface with coarse punctures but otherwise with shiny surface (Fig. 6 ). Median lobe of aedeagus as in Fig. 18A, B . Shape of median lobe, bent evenly and fairly uniform in lateral view, in ventral view pointed at apex. Parameres bi-segmented, elongated, and with few setae at apex (Fig. 18C, D ).

Female. Unknown.

Affinities.

This species is similar to G. pictipes but readily separated by the different colour pattern and the more flattened body. Furthermore, both species can be separated by the form of the median lobe and parameres (Figs 18 , 20 ).

Etymology.

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

Distribution.

A rare species, only known from the type locality on Kangaroo Island, South Australia (Fig. 22 ).

Habitat.

The single specimen was collected at the edge of the Eleaner River in the southern part of Kangaroo Island. Most probably this is not the original habitat of the species. Almost all Gibbidessus inhabit more seasonal, open wetlands, overgrown with sedges and rushes.

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 18, 19. 18 Gibbidessus kangarooensis sp. nov. 19 G. pederzanii 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 20, 21. 20 Gibbidessus pictipes 21 G. rottnestensis 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.