Eupotemus tuberculatus, Bilton & Bird, 2023

Bilton, David T. & Bird, Matthew S., 2023, Eupotemus tuberculatus sp. nov., the first hooded shore beetle confirmed from southern Africa (Coleoptera, Epimetopidae), Zootaxa 5339 (2), pp. 196-200 : 197

Eupotemus tuberculatus sp. nov.

( Figs. 1–2 )

Type locality. South Africa, North West Province, Magaliesberg, Mountain Sanctuary Park , margins of small mountain stream, -25.837929°, 27.468740°, 1430 m.

Type material. Holotype (male): “ 16/ii/2023 South Africa NWP// Magaliesberg – stream in// Mountain Sanctuary Park // -25.837929°, 27.468740°, 1430 m // D T Bilton leg.” and red holotype label ( AMG).

Paratype: 1m #, same data as holotype and red paratype label ( CBP) .

Description. Size: Holotype: BL 2.90 mm; EL 1.90 mm; EW 1.60 mm. Paratype: BL 2.75 mm; EL 1.80 mm; EW 1.50 mm.

Dorsum ( Fig. 1 ) predominantly dark chestnut brown to black; palpi and antennae straw yellow, last antennal segment darker; femora reddish, tarsi orange-brown. Front of head and pronotal and elytral margins paler. Venter dark reddish brown; labium paler. Paratype is somewhat paler due to tenerality. Habitus and sculpture as in Fig. 1A– C . Lateral ridge of the pronotum narrowly interrupted in middle. Ridge on elytral interval 3 complete throughout. Ridge on interval 5 interrupted anteriorly and posteriorly: short ridge present around shoulder, followed by interruption over approx. 1/6 of elytral length; ridge present over following 1/2 of elytral length, lower posteriorly; interrupted again after posterior declivity, with distinct, isolated tubercle approx. halfway to elytral apex. Ridge on elytral interval 7 complete to posterior declivity, then obsolete, with isolated tubercle(s) posteriorly, final one being continuous with tubercles on interval 9. Elytral interval 9 with two short ridges, one positioned appro x. 1/3, the other approx. 2/3 along elytral length; apically with tubercles continuous with those on interval 7. Elytral punctures connected by low elevated line.

Aedeagus ( Fig. 1D–F ): 0.85–0.92 mm long. Parameres ca. 1.9× longer than phallobase, constricted subapically, widened at apex. Median lobe 3.5× longer than wide, apical part narrowing in apical fourth, sides of median lobe narrowing to apex in a straight line. Phallobase basally with narrow symmetrical manubrium.

Differential diagnosis. The new species clearly belongs to the Eupotemus carinaticollis group sensu Fikáček et al. (2021), based on the lateral ridge of the pronotum being interrupted in the middle and similarities in aedeagal anatomy. Based on the Holotype and Paratype, E. tuberculatus sp. nov. would be readily distinguished from other member of the group by the strong posterior elytral tubercles and the pattern of development of elytral ridges. Posterior tubercles are present in both known specimens, but slightly less strongly developed in the paratype than the holotype. Given that Fikáček et al. (2021) note that elytral sculpture can be variable in long series, the most reliable means of identification is the form of the aedeagus. This has the same basic design as seen in other members of the carinaticollis group, and shares paramere apices which are flattened in dorsal and ventral views with E. carinaticollis ( Basilewsky, 1956) and E. taianus Fikáček et al., 2021 . Compared to these species E. tuberculatus sp. nov. has a less pronounced lateral constriction in the parameres, and a somewhat broader, more rounded apex to the median lobe. For comparative features of aedeagi in the group see Table 1 .

Etymology. Named in reference to the tuberculate elytral dorsum, particularly posteriorly.

Distribution and ecology. This is the first epimetopid confirmed from southern Africa. Geographically, the closest known species are E. carinaticollis from Democratic Republic of Congo and Burundi and E. uluguru Fikáček et al., 2021 from Tanzania ( Fig. 2A ). Hebauer (1999) notes a single specimen from Zimbabwe he attributed to E. carinaticollis in the Hungarian Natural History Museum, Budapest. Assuming this record is correct, the specimen may belong to E. tuberculatus sp. nov., or another, as yet undescribed, species. Fikáček et al. (2021) did not see this specimen, despite examining material from Budapest, and enquiries about this specimen by DTB have proved fruitless. E, tuberculatus sp. nov. is known currently from a single stream within a private nature reserve (Mountain Sanctuary Park) in the Magaliesberg, north of Johannesburg, South Africa.The Magaliesberg Formation is an ancient (ca. 2.1 Ga) mountain range ( Parizot et al. 2005), extending for approximately 150 km from Pretoria in the east to Rustenburg in the west. Due to the patchy nature of the geology of the region, headwater streams can have either quartzitic (sandstone) or dolomitic origin, with the collection site being a typical small perennial dolomitic stream with approximately neutral pH. Both specimens were washed from marginal sand and gravels in a small lateral ebayment with partial shade ( Fig. 2B ). E. tuberculatus sp. nov. was taken together with Laccobius praecipuus Kuwert, 1890 (Hydrophilidae) and Hydraena biseptosa Perkins, 2014 (Hydraenidae) .

Figures

FIGURE 1. Eupotemus tuberculatus sp. nov., holotype.A) dorsal habitus; B) lateral habitus; C) fronto-dorsal view; D) aedeagus dorsal; E) aedeadus lateral; F) aedeagus ventral. Scale bars A–C) = 0.5 mm; D–F) = 100 μm.

FIGURE 2. Eupotemus carinaticollis group, confirmed distribution and habitat. A) Distribution of E. carinaticollis group species, red symbol = E. taianus Fikáček et al., 2021, green symbols = E. carinaticollis (Basilewsky, 1956), yellow symbol = E. uluguru Fikáček et al., 2021, blue star = E. tuberculatus sp. nov.; B) Type locality of E. tuberculatus sp. nov. South Africa, Northern Province, Magaliesberg, Mountain Sanctuary Park, margins of mountain stream, 1430 m – red arrow indicates area where specimens were found.