Gibbidessus pederzanii, 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 pederzanii sp. nov. Figs 7 , 12 , 19 , 25

Type locality.

Australia, Western Australia, creek around Nannup [33°58'S, 115°45'E].

Type material.

Holotype: Male, "Australia (WA) Nannup env. roadside creeks 1/12/98 Pederzani", "Holotype Gibbidessus pederzanii Hendrich, Watts & Balke des. 2020" [red printed label] (SAMA). Paratypes (13 exs.): All specimens with same data as holotype. Two specimens with " SAMA Database No 25-001593" and one with a yellow printed label “photographed” (CFP, CLH, SAMA, ZSM). All paratypes are provided with printed red paratype labels.

Diagnosis.

Medium-sized species which externally is characterised by a rounded habitus, without disruption between pronotum and elytron, and shiny, non-microreticulate dorsal surface with testaceous markings on elytra. Dorsoventrally rather arched. Without cervical line but rather a few punctures instead (Fig. 7 ).

Measurements.

Holotype: TL = 1.5 mm, TL-H = 1.3 mm, MW = 0.85 mm. Paratypes: TL = 1.5-1.6 mm, TL-H = 1.3-1.4 mm, MW = 0.85-0.95 mm.

Head: Ferruginous, around eyes almost black, without cervical line but rather a few punctures instead (Fig. 12B ). Coarsely punctate, rather shiny, weak microreticulation visible. 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, between striae, slightly darker, 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 less pronounced, basal pronotal plicae present. Striae moderately defined, almost 1/2 length of pronotum, slightly incurved.

Elytra: Dark brown with vague basolateral and apical area ferruginous (Fig. 7 ). Coarsely and densely punctate, shiny, microsculpture absent. Striae deeply impressed, straight but shorter than basal pronotal striae.

Ventral side: Ferruginous. Prothorax and abdomen paler than other parts. Metacoxae and metaventrite covered with larger punctures, surface shiny, without microreticulation. Abdominal ventrites with dense and finer punctures, shiny, microreticulation absent. Metacoxal lines almost straight, anteriorly not divergent. Epipleuron testaceous, with few coarse punctures, shiny, lacking microsculpture. Legs ferruginous with meta- and mesotarsi somewhat darkened.

Male. Dorsal surface with coarse punctures but otherwise with shiny surface (Fig. 7 ). Median lobe of aedeagus as in Fig. 19A, B . Shape of median lobe, almost straight and fairly uniform in lateral view, in ventral view rounded at apex. Parameres bi-segmented, elongated, and without setae at apex (Fig. 19C, D ).

Affinities.

This species is similar to G. davidi sp. nov. but readily separated by the different colour pattern, the more roundish body (Figs 4 , 7 ), the larger punctation on elytra, and the form of the median lobe and parameres (Figs 16 , 19 ).

Etymology.

The species is named after our colleague, the dytiscid specialist Fernando Pederzani (Ravenna, Italy), who collected the type material. The specific epithet is a substantive in the genitive case.

Distribution.

South-western Australia. A rare species, which is only known from the type locality somewhere around Nannup in south-western Australia. Most probably a more inland species and restricted to forested areas and not in heathland or coastal sedge swamps (Fig. 25 ).

Habitat.

All specimens were collected in shallow water at the edge of a small slow flowing forest creek (F. Pederzani in litt.).

Figures

Figure 12. Head of G. davidi sp. nov. A with cervical line (red arrow), and head of G. pederzanii sp. nov. B without cervical line but rather a few punctures instead (red arrow).

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 24, 25. Distribution of 24 Gibbidessus pictipes (black dots) 25 G. pederzanii sp. nov. (red dot), G. rottnestensis sp. nov. (blue dots).

Figures 1 - 4. Habitus of 1 Gibbidessus atomus sp. nov. 2 G. chipi, 3 G. davidi, male 4 G. davidi female. 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.