Gibbidessus Watts, 1978

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

Genus Gibbidessus Watts, 1978

Gibbidessus Watts, 1978: 29; gender masculine; type species: Gibbidessus chipi Watts, 1978: 52 by original designation; Biström (1988: 19); Nilsson & Hájek (2020: 108).

Type species.

Gibbidessus chipi Watts, 1978.

Diagnosis.

Very small diving beetles (1.15-1.9 mm). The smallest epigean dytiscids in Australia can be found in this genus. Body oblong-oval or elongate and fairly compactly built. Head with or without cervical line; frontally not bordered. Palpi rather slender, apically very finely bifid, in one species broad. Pronotum with a pair of basal striae. Elytron with a basal stria but without sutural striae. Punctation of elytra does not form rows. Epipleura lack a basal cavity posteriorly limited by a transverse carina. Prosternal process rather elongate, narrow, laterally distinctly marginated and with ventral surface not medially excavated. Prosternal process reaches metaventrite, which is not distinctly depressed posterior to mesocoxae. Metacoxal lines comparatively short, only slightly longer than distance between them posteriorly. Very fine punctures on either side of midline of metaventrite, not forming distinct rows. Metatrochanters and metafemora not distinctly modified ( Biström 1988; Hendrich et al. 2019). Parameres symmetric. Larvae unknown.

Gibbidessus was described as a monotypic genus to accommodate G. chipi Watts, 1978. A molecular phylogenetic investigation covering all Australian Bidessini genera ( Hendrich et al. 2010) recovered G. chipi , the single Uvarus species reported from Australia, Uvarus pictipes (Lea, 1899), as well as three undescribed species in one clade (Fig. 26 ). We refer to this clade as genus Gibbidessus . Subsequently, we assembled a multigene dataset of global Hydroporinae (Balke, work in progress), where we again recovered Gibbidessus species as well as Uvarus pictipes in one clade. The non-Australian Uvarus included in that preliminary study did form a separate, not closely related clade. Consequently, Uvarus pictipes is transferred to Gibbidessus here.

Figures

Figure 26. Maximum likelihood tree for Australian Gibbidessus. Neighbour joining tree (p-distances) calculated with Geneious (11.0.4.) software.