Spanglerodessus Miller and Garcia

Miller, Kelly B. & Garcia, Mauricio, 2011, Spanglerodessus shorti and Incomptodessus camachoi, new genera and species of Bidessini from Guyana and Venezuela (Coleoptera: Dytiscidae: Hydroporinae), Zootaxa 2996, pp. 49-56 : 50

Spanglerodessus Miller and Garcia , new genus

( Figs. 1 –6,10,11)

Type species. Spanglerodessus shorti Miller and Garcia , new species, by present designation.

Diagnosis and description. This genus differs from others in the tribe by the combination of: 1) transverse occipital line absent ( Fig. 1 ), 2) basal pronotal striae present ( Fig. 1 ), 3) basal elytral stria absent ( Fig. 1 ), 4) elytral sutural stria faintly present in some specimens, 5) anterior clypeal margin unmodified, 6) elytron without longitudinal carinae ( Fig. 1 ), 7) epipleuron without transverse carina at humeral angle, 8) lateral lobes of aedeagus two-segmented ( Figs 4, 6 ), 9) habitus robust, short, lateral margins of pronotum and elytron conspicuously rounded ( Fig. 1 ), and 10) lateral bead on pronotum broad ( Fig. 1 ). Individuals lack natatory setae on the legs, which are robust and spinous, in general ( Fig. 3 ).

Etymology. The genus name is formed from a combination of “ spangler ” in honor of the great water beetle worker and friend, Paul J. Spangler, and “ dessus,” a common root in other genus names in this tribe.

Distribution and habitat. Spanglerodessus is known from the following newly described species from the Kumu Falls in Guyana and nearby localities in Venezuela ( Fig. 11 ). Label data indicated that specimens were collected in pools at the base of Kumu Falls.

Discussion. In addition to the species described here, four specimens of what appears to be another new species in this genus are in the USNM. These specimens are represented by only females and, so, are not described here. The specimens were found at the same site as Spanglerodessus shorti . Whereas that species was found in “side pools at base of falls,” label data indicate the specimens of the other species were collected from “wet boulders,” possibly a distinctly different microhabitat.

This genus keys to Bidessodes Régimbart in Biström’s (1988) key to the Bidessini genera of the world. Spanglerodessus specimens are considerably more robust than members of Bidessodes , which are elongate. Additionally, Bidessodes species are pale in coloration, typically with longitudinal yellow fasciae and conspicuous iridescence on the elytra, and have the lateral bead on the pronotum very narrow. Despite these numerous differences, it seems likely that Bidessodes may be closely related to Spanglerodessus . Spanglerodessus may also be closely related to the recently described Fontidessus Miller and Spangler , but Spanglerodessus are considerably more robust and lack natatory setae on the legs. Nevertheless, given the habitat and morphology of Spanglerodessus , which are quite similar to Fontidessus , it appears Spanglerodessus may be closely related to that genus. It is always a difficult challenge to decide whether to create a new genus or expand the definition of an existing genus in such circumstances. This problem is particularly acute in Bidessini where the many genera are defined by a few characters which occur in combinations clearly implying considerable homoplasy. Miller and Spangler (2008) and Balke and Ribera (2004) (among others) pointed out some of the serious problems with the distribution of the few characters (particularly the transverse occipital line) and their degree of homoplasy in the tribe. Nothing short of a comprehensive phylogenetic analysis of Bidessini with broad taxon sampling and extensive molecular data will likely help clarify how general these features are distributed and in what combination. In this case, we believe that, for now, a new genus is warranted in the absence of a comprehensive cladistic analysis of the tribe to help determine character distributions in a phylogenetic context.

Figures

FIGURES 1 – 9. Figs 1 – 6. Spanglerodessus shorti. 1, dorsal habitus, bar = 1.0 mm. 2, prosternal process. 3, right metathoracic leg, ventral aspect. 4 – 6, male genitalia, 4, median lobe and right lateral lobe, dorsal aspect, 5, median lobe, left lateral aspect, 6, left lateral lobe, left lateral aspect. Figs 7 – 9. Incomptodessus camachoi. 7, dorsal habitus, bar = 1.0 mm. 8, male median lobe and right lateral lobe, right lateral aspect. 9, male median lobe, ventral aspect.

FIGURES 11 – 14. Habitats. 11, Spanglerodessus shorti, AS- 08 - 058. 12 – 14, Incomptodessus comachoi; 12, VZ 09 - 0114 - 01 C; 13, VZ 09 - 0112 - 01 B; 14, VZ 09 - 0115 - 01 D. Codes correspond to collection locality codes listed in “ Material examined ” section for each species.