Nilssondytes, Miller & Michat & Ferreira Jr, 2024

Miller, Kelly B., Michat, Mariano C. & Ferreira Jr, Nelson, 2024, Description of Nilssondytes diversus gen. et sp. nov. from Venezuela (Coleoptera, Adephaga, Dytiscidae, Cybistrinae), ZooKeys 1210, pp. 325-332 : 325-332

Nilssondytes gen. nov.

Figs 1–10 , 11

Remark.

The following description is reproduced with some modifications from Miller et al. (2024).

Type species.

Nilssondytes diversus sp. nov., by current designation.

Diagnosis.

From other Cybistrinae this genus differs in having: (1) the metatibial spurs apically simple, (2) metacoxal lines clearly present, (3) the pronotum and elytron with broad, distinct lateral yellow bands along margins (Fig. 1 ), (4) males and females each with two metatarsal claws, the posterior much reduced in both sexes (Figs 2 , 3 ), (5) the prosternum and prosternal process relatively shallowly but distinctly sulcate (Fig. 4 ), (6) the medial margins of the male sternite IX straight, not emarginate (Fig. 10 ), (7) no cluster or line of setae at the apicodorsal angle of the posterior surface of the mesotarsomeres (Fig. 5 ), and (8) the ventral surface of the metatrochanter with an oblique, transverse groove. The single species in this genus (described below) is somewhat similar in size, shape, and coloration to Metaxydytes laevigatus (Olivier) and may be present among series of that species in collections. Nilssondytes differ from M. laevigatus in several features (see above) including the presence of yellow lateral elytral margins (Fig. 1 ) which are absent in M. laevigatus. Larvae are unknown.

Etymology.

This genus is named Nilssondytes from the Greek dytes meaning “ diver, ” and Nilsson, after the great diving-beetle worker and excellent friend, Anders N. Nilsson, in honor of his inestimable contribution to the science of diving-beetle biology.

Phylogenetic relationships.

The single species of Nilssondytes gen. nov. is part of the clade that includes species with an oblique metatrochanteric groove, but it has an unresolved position with respect to other genera ( Miller et al. 2024). The presence of a reduced posterior metatarsal claw in both males and females (Figs 2 , 3 ) with straight medial margins of the male abdominal sternite IX (Fig. 10 ) is a unique combination of features within Cybistrinae . Unique among this larger clade is also the sulcate prosternum and prosternal process (Fig. 4 ) which is somewhat similar to the Australian genera Spencerhydrus Sharp, 1882 and Sternhydrus Brinck, 1945 .

Figures

Figure 11. Distribution of Nilssondytes diversus sp. nov. in northern South America.

Figures 1–10. Nilssondytes diversus sp. nov. 1 dorsal habitus 2, 3 metatarsal claws, posterior aspect: 2 male 3 female 4 prosternal process, ventral aspect 5 right mesothoracic leg, posterior aspect 6–8 male genitalia: 6 median lobe, ventral aspect 7 median lobe, right lateral aspect 8 right lateral lobe, right lateral aspect 9 female genitalia (gonocoxae, laterotergites, right gonocoxosternite and internal genitalia), ventral aspect 10 male sternite IX, ventral aspect. Scale bars: 5.0 mm (1); 1.0 mm (2–5, 9, 10)