Tazarcus, Grebennikov, 2020

Grebennikov, Vasily V., 2020, Tazarcus, a new phylogenetically unplaced genus of two flightless weevils with metapleural ridge from the Eastern Arc Mountains, Tanzania (Coleoptera: Curculionidae: Molytinae), Zootaxa 4766 (3), pp. 421-434 : 425-426

Tazarcus gen. n.

http://zoobank.org/ urn:lsid:zoobank.org:act:09E4CE1E-BFE6-47E9-89BD-2A529F652DA4

Type species. Tazarcus aeaea sp. nov., here designated.

Diagnosis. Known representatives of the new genus can be recognized among weevils by the unique combination of the following easily observed characters: body small (combined dorsal length of pronotum and elytra 2.0– 3.4 mm); ratio of combined pronotal and elytral length in dorsal view to the maximal body width 1.6 x or less; elytra laterally rounded, without shoulders; rostrum relatively short and straight; eyes present, small and flat; antennal funicle with seven segments; anterior margin of prothorax laterally without postocular lobes; prosternum with canal laterally delimited by ridges tapering anteriad and linking anterior edge of prosternum with anterior edge of procoxae (thus canal only present in front of procoxae, not behind); procoxae separate; metanepisternal sutures absent, their place occupied by longitudinally oriented metapleural ridge bearing on its crest a line of short and robust small setae (sclerolepidia?); femora without teeth-like projections; tarsal claws small, separate and not appendiculate; elytra with nine longitudinal punctate striae; legs and rostrum dorsally covered with dense matt whitish pilosity; hind wings absent.

Adults of the new genus (particularly those of the type species) habitually resemble comparably rounded, flightless and globular members of the distantly related ( McKenna et al. 2009) genus Ocladius Schönherr, 1825 ( Meregalli & Colonnelli 2006). At least three Ocladius species have been reported from the highlands of northern Tanzania ( Aurivillius 1910), one of them ( O. seriatus Faust, 1896 ) from “Usambara”. Adults of Tazarcus are externally distinguishable from those of Ocladius by the straight, shorter and thicker rostrum lacking longitudinal keels and furrows.Adults of all other genera of flightless East African Molytinae have a more slender body (a ratio of dorsal combined length of pronotum and elytra to the maximal body width of> 1.6x). Four additional diagnostic characters aid in the identification of Tazarcus : (1.) small body size, combined length of pronotum and elytra in dorsal view 2.0– 3.4 mm; (2.) a short and straight rostrum; (3.) small flat eyes; and (4.) a short prosternal canal, tapering anteriad.

Species composition and distribution. This genus consists of two herein described allopatric species restricted to the EAM Chain in Tanzania. The two species can be easily separated by the form of the elytral punctation ( Figs. 1A, B vs Fig. 2A, B ).

Biology. Adult specimens of the new genus were found by sifting forest floor litter in wet Afromontane forests at elevations between 1576 m and 2318 m. Host plants, immature life stages, parasites or any other biological aspects are unknown.

Etymology. Toponymic, formed by abbreviating “Tanzanian Arc”, with reference to the EAM occurring predominantly in Tanzania; gender masculine.

Figures

FIGURE 1. Distribution of the genus Tazarcus gen. nov. detected in three (among 14, indicated by circles) sampled Tanzanian forests. Map designed using online SimpleMappr tool (Shorthouse 2010).

FIGURE 2. Other Molytinae weevils with metapleural ridge (ridges are magnified on the images below).