Nartus Zaitzev, 1907

Balke, Michael, Hájek, Jiří & Hendrich, Lars, 2017, Generic reclassification of species formerly included in Rhantus Dejean (Coleoptera, Dytiscidae, Colymbetinae), Zootaxa 4258 (1), pp. 91-100 : 97

Nartus Zaitzev, 1907 , status re-instated

Nartus Zaitzev, 1907: 103 ; type species: Dytiscus grapii Gyllenhal, 1808: 505 by monotypy.

Diagnosis. Medium sized (9–12 mm) species. Medial labral emargination shallow. Sides of pronotum mostly distinctly bordered except for anterior angles; base of pronotum strongly sinuate, thus posterior angles of pronotum produced backwards, acute ( Fig. 4A , arrow). Elytral reticulation double, consisting of large polygonal meshes filled with fine polygonal cells. Setae on parameres distally acute. In contrast to most species of Rhantus and related genera, both members of Nartus are totally black.

Position. In Morinière et al. (2016), Nartus was recovered as the sister group of Rhantus as newly defined here, and we suggest that the original use of Nartus at generic rank is justified by our studies ( Fig. 1 ).

Species composition. Holartic genus comprised of two species:

Nartus grapii ( Gyllenhal, 1808) , Europe ( Fig. 4A ).

Nartus sinuatus (LeConte, 1862) , Canada, northern USA.

Figures

FIGURE 1. Phylogenetic reconstruction of Colymbetinae relationships using different methods of phylogenetic inference (Bayesian, Maximum Likelihood, Parsimony, figure modified from Morinière et al. 2016 which contains more details on analytical procedures); node support for major backbone nodes indicated with asterisks: black meaning strong support, lighter shades of grey referring to increasingly weaker support. Distribution is coded in colour and ancestral areas were inferred using the software package BioGeoBEARS (details in Morinière et al. 2016). Notes: " R. signatus JFern. " refers to a specimen from Juan Fernandez Archipelago (originally described as R. kuscheli Guignot, 1952).

FIGURE 4. A) Nartus grapii (Gyllenhal, 1808), 11 mm, Germany; B) Rhantus atricolor (Aubé, 1838), 15 mm, Mexico; C) Rhantus frontalis (Marsham, 1802), 10.5 mm, Germany; D) Rhantus selkirki Jäch, Balke & Michat, 2014, 6.6 mm, Chile.