Fontidessus Miller & Spangler, 2008

Miller, Kelly B. & Montano, Elizabeth T., 2014, Review of the genus Fontidessus Miller & Spangler, 2008 (Coleoptera, Dytiscidae, Hydroporinae, Bidessini) with description of four new species, ZooKeys 426, pp. 65-85 : 66-67

Taxon classification Animalia Coleoptera Dytiscidae

Fontidessus Miller & Spangler, 2008

Fontidessus Miller & Spangler, 2008: 46.

Type species.

Fontidessus toboganensis Miller & Spangler, 2008 by original designation.

Diagnosis.

Fontidessus differs from other Bidessini by the combination of: 1) a transverse occipital line across the head absent (Figs 1-9), 2) a pair of basal pronotal striae present (Figs 1-9), 3) a basal elytral stria absent (Figs 1-9), 4) an elytral sutural stria faintly present in some specimens (e.g. Figs 4, 5), 5) the anterior clypeal margin unmodified, evenly rounded 6) the elytron without longitudinal carinae, 7) the elytral epipleuron without a transverse carina at the humeral angle, 8) the prosternal process variable in shape (Figs 10-16), but extending to metaventrite, 9) the metatrochanter extremely large relative to the metafemur, approximately 0.6 × length of metafemur (Figs 17-23), 10) overall, the habitus elongate to oval, and the lateral pronotal and elytral margins nearly continuously and shallowly curved (Figs 1-9), and 11) the lateral lobes of the aedeagus two-segmented (Figs 24-30). In addition, a new character was identified based on new material with better-preserved male genitalia. Species of Fontidessus have a distinctive ventral sclerite associated with the male median lobe. In most species, this sclerite is short and oval (Figs 26B, 28-30B), but in Fontidessus toboganensis and Fontidessus aquarupe it is elongate (Figs 25B, 27B). In Fontidessus microphthalmus , though, the median lobe is complex with large dorsal and ventral portions (Fig. 24). The dorsal part may be homologous with the dorsal sclerite of other taxa. This species is different in several respects from other Fontidessus , and it is possible the ventral portion of the median lobe is, however, not homologous with the ventral sclerite in other taxa. Fontidessus is similar to Spanglerodessus Miller & García, but that genus lacks natatory setae (a possibly derived condition based on life in hygropetric habitats where swimming is not so important) and has a body that is very robust with the lateral pronotal margins extremely broadly expanded and rounded with the lateral margin of the body distinctly discontinuous between the elytron and pronotum. Also, the male median lobe of the single species, Spanglerodessus shorti Miller & García, does not have the distinctive ventral sclerite of Fontidessus . Nevertheless, the two genera appear to be similar.

Natural history.

All the known species of Fontidessus are hygropetric (Figs 34-36), and most are known from only one or few localities. They are characteristic of marginal and small aquatic habitats on inselbergs or other rock surfaces (Figs 34, 36) and the margins of waterfalls (Fig. 35) in the Guaiana Shield region of northern South America (Figs 31-33). They can often be extremely abundant in these habitats. Several of the species co-occur, but others are the only known species at some sites (Figs 31-33).

Discussion.

Two previously described species, Fontidessus ornatus and Fontidessus wheeleri , were based on few specimens. Each of the male holotype specimens had been previously dissected, and it clearly appears, based on acquisition and examination of new material, that the male median lobes had been switched between the two and each median lobe suffered some damage during its dissection. Therefore, the incorrect male genitalia were associated with each species in the original descriptions, and the descriptions of these structures were based on somewhat damaged material ( Miller and Spangler 2008). This is corrected in the following treatments.

Checklist of Fontidessus species

Fontidessus Miller & Spangler, 2008

Fontidessus aquarupe Miller & Montano, sp. n.: Guyana.

Fontidessus bettae Miller & Montano, sp. n.: Venezuela.

Fontidessus christineae Miller &Montano, sp. n.: Suriname.

Fontidessus microphthalmus Miller & Montano, sp. n.: Suriname, Venezuela.

Fontidessus ornatus Miller in Miller and Spangler 2008: Guyana, Suriname, Venezuela.

Fontidessus toboganensis Miller & Spangler, 2008: Suriname, Venezuela.

Fontidessus wheeleri Miller in Miller and Spangler 2008: Venezuela.