Riberazantaena, Bilton, 2021

Bilton, David T., 2021, Riberazantaena, a new hydraenid genus from the Eastern Arc Mountains of Tanzania (Coleoptera, Hydraenidae), Zootaxa 4999 (6), pp. 573-581 : 575-577

Riberazantaena new genus

Type species: Protozantaena grebennikovi Perkins, 2009: 47 , herein designated.

Differential diagnosis. Recognized by the following combination of characters: size small (length ca. 1.70–1.95 mm); body form flattened; antenna ten-segmented (five + club); maxillary palpi relatively short ( Fig. 1 ); no hypomeral carina; hypomeral antennal pocket setae forming a strong cup; ocelli weakly developed, located between the midline and the eyes; pronotum transverse with anterior hyaline margin and without postocular emarginations; elytral series striate impressed; tarsi relatively short and aedeagus simplified with a single, terminal flagellum. Distinguished from Parhydraena and Decarthrocerus by the lack of a hypomeral carina, and the very small size. Distinguished from Discozantaena by the very small size, the presence of well-developed hypomeral antennal pocket setae, and the markedly different habitus. Distinguished from Parhydraenopsis by the very small size, the less convex body form, the different elytral puncture pattern, and differences in aedeagal anatomy. Distinguished from Protozantaena by the relatively short maxillary palpi (palpus length/head width ca. 0.4) and short tarsi (see Fig. 1 ), the striate impressed elytral series and the absence of parameres on the aedeagus (see Fig. 2 ).

Description. Body size small, length ca. 1.70–1.95 mm; form elongate oval, weakly transversely convex dorsally, head not deflexed. Antennomeres ten (five + club), second slightly longer than combined lengths of third to fifth. Maxillary palpi relatively short; palpus length/head width ca. 0.4. Eyes well-developed, not elevated, 6–8 facets in longest series in dorsal aspect. Labrum set at an angle to clypeus, slightly longer than clypeus, anterior margin distinctly emarginate. Clypeus anterior margin and frontoclypeal suture arcuate. Ocelli weakly convex, located midway between midline and eyes. Frons very weakly convex between ocelli; area behind and between ocelli lacking carinae. Pronotum with anterior and posterior shallow transverse impressions on disc, posterior impression usually U-shaped; anterior hyaline border present over median third, narrow. Hypomeron lacking carina at margin of hydrofuge pubescence; antennal pockets well developed, bordered by row contiguous, arcuate setae forming strong cup, numbering ca. 16–18. Proventral antennal cleaner, a dense cluster of sharp spines, located on anterolateral margin of each side of prosternum. Mesoventrite with well-developed midlongitudinal and lateral ridges and truncate posterior intercoxal process. Metaventrite with shallow impression on disc in basal 1/2, and midlongitudinal carina between impression and mesoventral intercoxal process. Each elytron with ten striate impressed rows of punctures, six between suture and humerus; serial punctures deeper and larger than punctures on intervals, setae slender and rather short. Legs, including tarsi, relatively short; basal three pro and mesotarsomeres with well-developed suction setae in both sexes (although larger in males); those of protarsi larger than on mesotarsi. Intercoxal sternite small, triangular. Aedeagus simplified, with gonopore at tip of long, fine flagellum; parameres absent, reduced to setae on base of main piece.

Etymology. Named in memory of my recently departed friend and colleague, Ignacio Ribera, who was originally intended to be a co-author of this work. Ribera is used in combination with zantaena from Protozantaena . Gender feminine.

Figures

FIGURE 1. Habitus images of A) Riberazantaena grebennikovi, Uluguru Mountains, Tanzania; B) Riberazantaena latissima sp. nov., Chome Forest, South Pare Mountains, Tanzania. Scale bar = 1 mm.

FIGURE 2. Aedeagi of A) Protozantaena labrata, modified from Perkins (2009); B) Protozantaena palpalis, modified from Perkins (2009); C) Riberazantaena grebennikovi, Uluguru Mountains, Tanzania; D) Riberazantaena latissima sp. nov., Chome Forest, South Pare Mountains, Tanzania. Scale bar = 0.1 mm. Note that the flagella of P. labrata and Riberazantaena spp. are flexible, meaning that curvature etc. is not diagnostic.