Gibboryctes Endrödi, 1974: 13

Costa, Leidiane O., Duarte, Paulo R. M., Iannuzzi, Luciana & Grossi, Paschoal C., 2022, Taxonomic revision and notes on natural history of the enigmatic beetle genus Gibboryctes Endrödi (Coleoptera: Melolonthidae: Dynastinae), Journal of Natural History 56 (1 - 4), pp. 191-225 : 193-202

Gibboryctes Endrödi, 1974: 13

Type species

Gibboryctes szelenyii Endrödi, 1974 (by monotypy).

Diagnosis

Gibboryctes is separated from other Neotropical Oryctini by the following combination of characters: inconspicuous sexual dimorphism ( Figures 1 (d–f) and 3(a–c)); transverse head, 2 times wider than long ( Figure 9 (a,b));both sexes with a transverse tubercle on head ( Figures 9 (a,b) and 11(a–c)); bidentate mandibles with subapical tooth backward produced and larger than apical tooth ( Figure 7 (a–c)); inner margin of galea bearing small teeth; pronotum with no horns,with only a small tubercle on anterior area combined with a shallow or absent concavity ( Figures 9 (a,b) and Figures 11 (a–c)); elytra with dense, large and deep punctures ( Figure 12 (b,d,f)); ventrite VI 2 times longer than ventrite V in female ( Figure 13 (a–c)).

Generic redescription

Length: 21.0– 35.6 mm. Width: 11.0– 16.9 mm. Poorly apparent sexual dimorphism; body elongated, oval in dorsal view, convex in lateral view; dorsal surface nearly completely glabrous; ventral surface densely setose. Colour: From dark reddish brown to dark. Head: Transverse, about 2 times wider than long. Clypeus triangular, short, about 4 times wider than long, slightly narrow laterally, anteriorly acute; surface coarsely rugose, with scattered setae on each side. Frontoclypeal suture with a short, transverse, sometimes emarginate, subtrapezoidal tubercle. Frons from flattened to slightly concave; from rugopunctate to densely punctate. Ocular canthus rectangular, transverse, glabrous. Antennae: Provided with 10 segments; club short, globular, subequal in length to antennomeres II–VII combined; club decreasing in size from basal to apical lamella. Mouthparts: Labrum from trapezoidal to parabolic in shape. Mandibles with 2 rounded teeth (1 apical, 1 subapical) on outer margin; teeth projected forward beyond clypeus in dorsal view, strongly reflexed above clypeus in lateral view; subapical tooth slightly backward produced, larger in size compared to apical tooth. Maxillae with small teeth at inner margin of galea; stipe produced laterally in triangular shape. Labium oval, densely covered with bristled punctures. Thorax: Pronotum weakly convex in lateral view; horn absent, but with a small tubercle located at middle area contiguous to anterior margin; dorsal surface nearly completely covered with dense, large, deep, ocellated punctures; discal area covered with large, coalescent punctures, sometimes longitudinally scattered along of a middle line; anterior and lateral borders complete, posterior usually incomplete. Scutellar plate from subtriangular to parabolic, bearing irregularly scattered punctures. Elytral surface with 8 wellmarked striae longitudinally (4 discal, 4 lateral); striae covered with a row of large, ocellated, deep punctures; interstriae with mixed fine and large punctures. Legs: Protarsi with scytheshaped claws; tarsomere V clavate, elongated, 2 times longer than tarsomere IV; tarsomeres I–IV ‘beaker’-shaped, subequal in length. Protibial outer margins with 4 teeth (1 apical, 2 medial, 1 basal); apical tooth triangular, curved, pointed; medial and basal teeth triangular; basal tooth smaller than previous ones; dorsal surface weakly punctate, longitudinally covered with a double row of bristled punctures. Mesotarsi similar to metatarsi, with tarsomeres I–IV gradually decreasing in size. Meso- and metatibiae cylindrical in shape, with 2 transverse carinae on outer surface (1 basal, 1 medial); carinae and apex weakly crenulated, covered with stout spinules like-setae; inner surface moderately covered with long bristles. Abdomen: Tergite VII lacking stridulatory apparatus. Tergite VIII transverse, subtriangular, strongly convex in lateral view in male; surface glabrous, rugopunctate on sides, densely covered with large, deep punctures on discal area. Ventrites II–VI coarsely rugopunctate on sides, finely punctate and glabrous on discal area; ventrites III–V with an incomplete row of setigerous punctures confined on sides; posterior margin of ventrite VI emarginate, setose. Aedeagus: Parameres, in dorsal view, symmetrical, basal half clearly wider than apical half, inner margin weakly bristled on apex. Parameres, in lateral view, 1.5 times shorter than phallobasis, dorsal surface convex, ventral surface with a weakly downward-produced carina at middle.

Sexual dimorphism

The two sexes are largely identical, but the female can be distinguished in the following aspects: Head: Anterior clypeal margin rounded. Abdomen: Tergite VIII flattened in lateral view; ventrite VI parabolic, lacking posterior emargination.

Specific composition

Gibboryctes comprises three species: G. szelenyii , Gibboryctes ebeninus sp. nov. and Gibboryctes endroedii sp. nov.

Figures

Figure 1. Gibboryctes szelenyii Endrödi, 1974. (a,b) Holotype male in dorsal and lateral views, respectively; (c) labels; (d,e) male habitus in dorsal and lateral views, respectively; (f) female habitus in dorsal view. (a,b) pictures out of scale.

Figure 7. Right mandible in dorsal view. (a) Gibboryctes szelenyii Endrödi; (b) Gibboryctes ebeninus sp. nov.; (c) Gibboryctes endroedii sp. nov.; (d) Heterogomphus gracilicornis Prell; (e) Tetragus waldenfelsi (Endrödi). Red arrows indicate the apical tooth in (a–e), striate molar in (d).

Figure 9. Detail of head, pronotum and prothoracic legs of males in dorsal view: (a) Gibboryctes szelenyii (Endrödi); (b) Gibboryctes endroedii sp. nov.; (c) Heterogomphus gracilicornis Prell; (d) Tetragus waldenfelsi (Endrödi).

Figure 11. Detail of head, pronotum and prothoracic legs of females in dorsal view: (a) Gibboryctes szelenyii Endrödi;(b) Gibboryctes ebeninus sp. nov.; (c) Gibboryctes endroedi sp.nov.; (d) Heterogomphus gracilicornis Prell; (e) Tetragus waldenfelsi (Endrödi). Arrow indicates punctate frons in (b).

Figure 12. Females of Gibboryctes species with detail of head, pronotum and prothoracic legs in lateral view and left elytra in dorsal view, respectively. (a,b) Gibboryctes szelenyii Endrödi; (c,d) Gibboryctes ebeninus sp. nov.; (e,f) Gibboryctes endroedii sp. nov. Jsi, juxtasutural interstria. Arrow indicates coalescent punctures in (e).

Figure 13. Detail of ventrites I–VI of females. (a) Gibboryctes szelenyii Endrödi; (b) Gibboryctes ebeninus sp. nov; (c) Gibboryctes endroedii sp. nov.; (d) Tetragus waldenfelsi (Endrödi). Red arrows indicate the proportions of ventrites V and VI.