Meridiorhantus, Balke, Michael, Hájek, Jiří & Hendrich, Lars, 2017

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

Meridiorhantus n. gen.

Type species: Dytiscus calidus Fabricius, 1792 by present designation.

Diagnosis. Medium sized to large (12–17 mm) species. Medial labral emargination deep. Sides of pronotum with border thin, often indistinct or partly lacking; posterior pronotal angles weakly obtuse elytral reticulation simple, consisting of fine isodiametric cells and without larger polygonal meshes. Setae on parameres apically acute, not modified to trumpet-shaped “suction” setae ( Balke 1990).

Position. Sister group of Carabdytes Balke, Hendrich & Wewalka, 1992 ( Morinière et al. 2016) ( Fig. 1 ).

Etymology. Composed from prefix Meridio -, derived from Latin meridiem (= southern) and stem Rhantus , genus of Colymbetinae ; gender masculine.

Species composition. Five species distributed in the southern Neotropical region, one of whĺch has two subspecĺes; the only exception is M. calidus (Fabricius, 1792) n. comb. which is widely distributed in the Neotropical Region and reaching also Nearctic regions in Mexico, the southern USA and the E coast of the USA as far north as New York City.

Meridiorhantus antarcticus (Germain, 1854) n. comb.

M. antarcticus antarcticus (Germain, 1854) , Chile ( Fig. 3 B).

M. antarcticus nahueli Trémouilles, 1984 , Argentina.

Meridiorhantus calidus (Fabricius, 1792) n. comb., South and Central America, West Indies , southern USA ( Fig. 3 C).

Meridiorhantus limbatus (Aubé, 1838) n. comb., Brazil

Notes: This species was not included in Morinière et al. (2016). It is morphologically however very similar to M. antarcticus and M. orbignyi ( Balke 1993a) which leads us to conclude that it belongs to this clade as well. Meridiorhantus orbignyi ( Balke, 1992) n. comb., Argentina, Brazil, Uruguay. Meridiorhantus validus (Sharp, 1882) n. comb. ( Fig. 3 D), Argentina, Chile.

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 3. A) Carabdytes upin upin (Balke, Hendrich & Wewalka, 1992), 12 mm, Papua New Guinea; B) Meridiorhantus antarcticus (Germain, 1854), 14 mm, Chile; C) Meridiorhantus calidus (Fabricius, 1792), 13 mm, Chile; D) Meridiorhantus validus (Sharp, 1882), 13 mm, Chile.