Griburella, Sassi, 2025

Sassi, Davide, 2025, A new genus of Pachybrachini from Bolivia (Coleoptera: Chrysomelidae: Cryptocephalinae), Zootaxa 5588 (3), pp. 455-464 : 456-458

Griburella gen. nov.

urn:lsid:zoobank.org:act:81BE0D1D-848D-4F1A-ACA8-840237463401

Type species. Griburella sanctaecrucis sp. nov., by monotypy.

Etymology. The generic name, which is feminine, is meant to highlight the proximity to the genus Griburius , with which the new taxon shows morphological affinities.

Description. Head: vertex and frontoclypeal surface matt, looking finely knurled, covered with close, shallow punctation and scattered, long, adpressed, whitish setae. Labrum surface fairly convex and slightly raised, so that in frontal view labrum looking markedly curved (Figs 2c, 3k). Eyes hugely developed, bulging, upper eye lobes in contact along midline in male, very close to each other in females (Figs 1c, 2c). No hints of ocular lines along ocular rims. Ocular canthus sharp with excision barely less than 90°, not differentiated in punctation and setosity from the remainder of frontoclypeal surface. Small subtriangular area (= ocular pit), slightly depressed, bare, mildly shiny, starting from antennal socket, obliquely directed towards median line (op in fig. 3k). Antennae slender, filiform, with antennomeres 3–5, sublucid, thin, rod-shaped; 6–11 dull, slightly more flattened and more diffusedly setose.

Pronotum: about one-third elytron length, trapezoid-like, at base margined and not crenulate, with sides slightly converging forwards. Pronotal surface moderately convex, dull, looking finely knurled, covered with extremely dense, regularly spaced, shallow punctures and equally arranged short, recumbent, whitish setosity. Lateral margins slightly expanded, moderately grooved, not visible from above, regularly and shallowly curved. Anterior and hind corners square, not projecting, with small setigerous tubercle. All corners with seta. Pronotal posterior margin at middle slightly impressed and slightly extended backwards.

Scutellum: strongly raised, almost square with apex truncated in straight line.

Elytra: combined together, approximately 1.3 times longer than wide. Elytral outline slender, parallel-sided. Humeral calli moderately prominent, impunctate. Elytral suture straight, entire. Elytral surface regularly convex, only feebly flattened at middle of disc. Postscutellar area not raised. Surface ornamentation very similar to pronotal one, dull, looking finely knurled, covered with extremely dense, regularly spaced, shallow punctures and equally arranged short, adpressed, whitish setosity. No real rows of punctures present. Lateral margins narrow, barely visible from above. On lateral view, bending on elytral side weakly pronounced. Epipleura not folded inward, flat, dull, internally delimited by weak edge only on anterior section, i. e. from basal margin up to middle of elytral bending, surface ornamentation not different from remainder of elytron.

Underside: hypomera almost bare, moderately shiny, basically impunctate. Remainder of ventral surface matt, covered with thick, short, regularly distributed, adpressed setae and shallow punctures. Procoxae separated. Prosternal process longer than wide, devoid of antennal grooves, relatively narrow with sides slightly sinuous; basal portion slightly concave; apical portion convex, weakly carinate, tapering to blunt tip slightly extending beyond posterior margin of prothorax. Surface covered with coarse, shallow punctures and long, curly setae.

Legs: (Fig.2d) with femora and tibiae in both sexes straight, slim.Male protibiae with reduced sexual dimorphism. Profemora similar in shape and size to median and rear ones. Mesotibie devoid of terminal spurs. Tarsomeres short, not particularly widened. Fifth tarsomere with blackish, clearly appendiculate claws.

Comparative notes. The new taxon proposed here possesses highly distinctive morphological characters that complicate its assignment to known genera. At first glance, it shows some resemblance to many species of the genus Griburius , particularly in the eye structure, with the eyes nearly meeting along the midline. However, closer examination reveals significant differences. The relatively slender silhouette, with the elytra approximately three times the length of the pronotum, and the shallow lateral elytral curvature set the new taxon apart from the typical Griburius shape. Even more remarkable is the presence of appendiculate tarsal claws, a unique feature, as this condition has not been observed in any other species of Pachybrachini . Other problematic traits include the morphology of the elytral epipleura. In closely related genera, the epipleura are clearly folded inward and have a sculpture distinct from that of the elytral surface. In Griburius and Metallactus Suffrian, 1866 the epipleural surface is smooth, flat, or slightly convex, lacking punctation or featuring only a few isolated punctures. In Pachybrachis , the surface is flat or slightly concave, and it almost always features a row of relatively deep punctures. In contrast, in Griburella , the epipleura are nearly vertically oriented, and the surface ornamentation is essentially identical to that of the elytral surface. In Griburella , the interocular distance in males is greatly reduced, a condition not uncommon among Pachybrachini and notably observed in Griburius , but also, though less pronounced, in many Pachybrachis species. However, and quite surprisingly, females in the new taxon also exhibit a significant reduction in interocular distance. Although more widely spaced than in males, the eyes in females are very close along the midline, whereas in other genera the female eyes are always well separated.Additionally, the prosternal process is particularly narrow, tapering posteriorly to a slightly carinate apex. In Griburius , the prosternal process is distinctly different, being broader with a flat surface and usually a broadly rounded apex. The shape of this structure is instead more similar to that observed in Metallactus and Pachybrachis , although in these genera the prosternal process is generally wider. Again, in male Griburella , the fore femora are not as strongly robust as in Griburius , nor do the tibiae and tarsi show marked modifications. Thus, there are no significant differences in leg morphology between males and females. In this regard, the condition resembles several species of Pachybrachis more than Griburius . Griburella also presents a small pit within the eye, with a slightly depressed, smooth and almost glabrous surface (Fig. 2c, op in fig. 3k). Although subtle, this condition does not appear to be present, to my knowledge, in any other Pachybrachini species, making it noteworthy, even if its phylogenetic significance cannot be assessed based on data from a single species. Also remarkable, the labrum in Griburella is strongly arched with a narrow and relatively deep median emargination (la in fig. 3k). In other Pachybrachini genera, the labrum is flat, with a proportionally broader median emargination. A further noticeable feature in Griburella can be observed in the female rectal apparatus (Fig. 3a), where the single ventral sclerite, whose apodemes are bent ventrally and not projected beyond rectus, is notably narrower than observed in other genera and is fully pigmented along its length. In related genera, the ventral sclerite is taller and is poorly pigmented in the central area.Additionally, the pigmentation of the dorsal sclerite is limited to the apodemes, and the apodemes do not extend beyond rectum and are bent dorsally. Figures 3b–d provide a comparative overview of the rectal apparatus among the type species of the genera: b: Griburius ( G. scutellaris (Fabricius, 1801)) , c: Metallactus ( M. kollari (Perty, 1832)) , and d: Pachybrachis ( P. hieroglyphicus (Laicharting, 1781)) . Also peculiar in the new genus is the shape of the tergite VIII (4a–c), which has a very narrow notch at the center of the posterior margin, bordered by a pair of small, pigmented, and slightly raised projections (rp in fig. 4c). In other genera, the posterior margin of the tergite VIII typically shows a broader indentation, lacking specific bordering structures. Finally, the dorsal surface ornamentation, consisting of extremely dense and fine punctation paired with equally dense short setae, is unlike that seen in any other currently known South American Pachybrachini species.

Further remarks. In the single available female specimen, the transverse, sinuous dorsal sclerite of the rectal apparatus has a short, pointed median projection directed posteriorly, a feature absent in other genera. However, further data are needed to confirm whether this characteristic is indeed diagnostic of the new genus.