Prototrupes Krikken, 1977

Gussmann S. M. & Scholtz, C. H., 2000, Systematic revision of endemic southern African genera of Bolboceratinae (Coleoptera: Scarabaeoidea: Bolboceratidae), Journal of Natural History 34, pp. 1045-1123 : 1053-1056

Prototrupes Krikken

(®gures 1a±m, 2a±c, 3, 24e)

Prototrupes Krikken, 1977a: 162 ; 1984: 31; D’Hotman and Scholtz, 1990: 25, ®gure 39 (Phyl.); Scholtz and Browne, 1996: 600 (Phyl.).

Type species: Bolboceras copridoides Kolbe, 1907 , by original designation.

Description

Body length. 14.9±25.5 mm.

Colour. Light brown but forebody darker (reddish to dark brown).

Head. Dorsal surface setose except for eye-canthus (®gure 1a±c). Outer margin of mandible rounded but anteriorly sharply curved inward (®gure 1a±c). Labrum (®gure 1a±c) ¯at, without transverse carina; distinctly setose; anterior margin straight. Clypeus, frons with three or four horns. Antennal club elliptic, massive, slightly longer than diameter of eye; apical segment strongly ināted (®gure 1d); outline of each segment ovoid; basal segment feebly convex; glabrous area of basal segment about one-third of exposed surface.

Pronotum. With four to six protrusions (®gure 2a, c); laterally with two arcuate ridges; lateral margin distinctly crenulate.

Scutellum. Very wide, basal width about 1.8Ölength, semi-circular (®gure 1e); ®nely to coarsely punctate.

Elytron. Anterior margin upturned; striae weekly to moderately impressed, their punctures small and separated by two to ®ve puncture diameters; intervals nearly ¯at, with very ®ne or small punctation; sutural stria terminating at scutellum in a straight line, second stria curving in toward scutellum but then obsolete and not reaching scutellum (®gure 1e).

Prosternum behind procoxae (®gure 1g). Simple, concave, without carina or spines.

Metasternum (®gure 1f). Process longitudinally keeled, widely separating mesocoxae; roundedly declivous anteriad; meso-metasternal suture absent.

Legs. Protibia strongly dilated, ®ve- to six-dentate (e.g. ®gure 2a). Protibial spur elongate, longer than ®fth tarsomere; acuminate. Protarsus with ®rst tarsomere always distinctly longer than ®fth tarsomere, equally long or longer than tarsomeres 2, 3 and 4 together. Metafemur in ventral view with line of densely spaced setose punctures in anterior third, otherwise with setose punctures spread over most of surface (as in Bolboceratex , ®gure 24e). Metatibia in lateral view strongly broadening from base to apex; with subapical carina unlobed; with small knoblike projections randomly spread over basal two-thirds of surface above subapical carina (®gure 1m). Metatarsus with many subapical setae on tarsomeres 2±4.

Underside. With extremely dense and long setation.

Male genitalia. Aedeagus as in ®gure 1h±j.

Distribution (®gure 3). Mainly dunes of the Namib and Kalahari deserts in Namibia, Botswana and South Africa.

Comments. The genus Prototrupes , consisting of only two species, is unique and most readily recognized genus not only of the southern African, but all African genera. Distinguishing features are the very long and dense setation, the presence of setation on the dorsal surface of the head, the large antennal club with the apical segment strongly ināted, the very wide semi-circular scutellum, the keeled and broad metasternal process, the absence of a meso-metasternal suture, the broadened protibia, the apically broadened meso- and metatibia and the elongate ®rst tarsomere of the protarsus. Krikken (1977a) stated that the elytral base of Prototrupes has a ®ne ridge. Subsequently, in the generic reclassi®cation (1984), he described the elytral base as being`marginate’ as opposed to`immarginate’. The latter terms, however, are misleading: all genera possess a basal elytral margin, only that in Prototrupes this margin is ridged and upturned whereas in other genera the elytral base is always slightly curved downward and thus virtually concealing the basal margin that is only feebly ridged.

Both Prototrupes species share identical aedeagi. The size of the aedeagus relative to the body size is very small. Figure 1h ±j illustrate the partially projected aedeagus of a Prototrupes kochi (Paulian) specimen. The parameres are simple and lobed, the pair of long, thin projections is part of the internal sac.

As already assumed by Krikken (1977a), some of the unique generic features of Prototrupes such as long setation, broadened tibiae, enlarged antennal club, might be adaptations to the extreme arid and sandy environment in which the genus occurs. Other, non-adaptive features such as shapes of the metasternum, the prosternum behind the procoxae, the scutellum and the aedeagus are indicative, we believe, of a phylogenetically truly isolated lineage in comparison with the remaining African genera.

Figures

FIG. 1. Prototrupes kochi: head dorsal view, male or female (a). Prototrupes copridoides: head dorsal view, male (b) and female (c). Prototrupes spp.: antennal club (d), scutellum and strial punctures (e), metasternum (f), posterior end of prosternum, frontal view (g). Prototrupes spp.: aedeagus, dorsal (h), ventral (i), lateral view (j). P. kochi: mesotibia, dorsal view (k). P. copridoides: mesotibia, dorsal view (l). Prototrupes: metatibia, lateral view (m). Scale bars in all ®gures5 1mm.