Truncaudum Hulcr and Cognato

Hulcr, Jiri, 2010, New genera of Palaeotropical Xyleborini (Coleoptera: Curculionidae: Scolytinae) based on congruence between morphological and molecular characters, Zootaxa 2717, pp. 1-33 : 24-25

Genus Truncaudum Hulcr and Cognato , gen. n.

Type species. Truncaudum impexum (Schedl)

Description. Eyes shallowly to deeply emarginate, upper portion of eyes smaller than lower part. Antennal club circular, club type two (obliquely truncated first segment, second segment visible on posterior side). First segment of club covering most of posterior face, margin of the first segment clearly costate all around the antenna, or mostly costate, may appear softer on posterior side. Second segment of club visible on both sides of the club, soft on posterior side, soft or corneous on anterior side. Third segment of club absent from or only partly visible on the posterior side of club. First segment of antennal funicle shorter than pedicel, funicle composed of 4 segments, scapus regularly thick. Frons rugged, coarsely punctate. Submentum deeply impressed, very narrow triangle. Anterior edge of pronotum with no conspicuous row of serrations (serrations don't differ from those on the pronotal slope). Pronotum from lateral view elongated, with low summit (type 7), from dorsal view elongated basic shape with rounded frontal margin (type 7). Pronotal disc shining or smoothly alutaceous, with small punctures, often richly pubescent. Lateral edge of pronotum obliquely costate. Procoxae contiguous, prosternal posterocoxal process tall and pointed. Mycangial tuft on pronotal basis or elytral absent. Scutellum flat, flush with elytra, or miniature, but always visible. Elytral bases straight, with oblique edge, elytral disc longer than declivity, flat, punctures on elytral disc in strial lines. Elytral declivity differs between T. agnatum , the most common Truncaudum , and all other Truncaudum spp. In T. agnatum , the lateral profile of elytral declivity is slightly convex, gradually sloped, dorsal profile of elytral apex rounded. Elytral declivity in T. agnatum is pubescent, often appearing rugose, with dense granules and punctures, posterolateral declivital costa absent, no tubercles on declivital interstria 2, several tubercles on interstriae 1 and 3, these often very dense, or in the form of spines. In all other members of the genus Truncaudum , declivity is sharply truncated, most often with pointed granules or large tubercles on declivital edge, and small tubercles inside the declivity on interstriae 1 and 3. Surface of declivity varies from shining and opalescent to coriaceous, granulate and conspicuously rugged. The rest of description applies to all species, including T. agnatum . First interstriae parallel on disc but broadened towards elytral apex, where they sometimes bear tubercles. Protibiae with evenly rounded edge, posterior side of protibia flat, with setae only. Protibial denticles small, bases of the denticles small to slightly enlarged, between 6 and 8 protibial denticles present. Most species reddish brown, darker towards abdomen. Entire body surface often richly pubescent. Length: 1.7-3.4 mm.

Diagnosis. The most characteristic feature of Truncaudum is the abruptly truncate elytral declivity, often surrounded by denticles. The genus is phylogenetically related to Amasa ( Fig. 8 , Cognato et al., 2011), but it differs from Amasa by the declivity surrounded with denticles, rich vestiture on most of body surface, elongated pronotal disc, and antennal club type 2. The unusual Truncaudum agnatum without truncated declivity can be mistaken with Xyleborus . T. agnatum has more abundant vestiture over its body, its declivity not surrounded by costa posteriad, and its prosternal posterocoxal process is slender and pointed. Truncaudum tuberculifer ( Eggers, 1923) and Amasa sirambeanus ( Eggers, 1923) bear combination of characters of both genera ( Fig. 8 ), and their placement remains uncertain.

Etymology. L, neuter, refers to truncated declivity. Gender-specific endings of many species in this group were uncertain since Wood and Bright (1992) moved a number of them from Xyleborus (masculine) to Cyclorhipidion (neuter). Neuter names from the Catalog ( Wood & Bright, 1992) have been disseminated broadly, thus we chose a new genus name with neutral gender.

Biology: The known species excavate a single short tunnel leading to often large terminal brood cavity.

Comments. Schedl, Eggers, and others erected a number of species based on minute differences of elytral declivity, which unlikely represent unique lineages.

Figures

FIGURE 8. A morphology-based cladistic analysis of species previously placed in Amasa, Cyclorhipidion, Xyleborus, and similar species of unclear affiliation. Combinable-component consensus of 240 most parsimonious trees (60 steps). The large number of MP trees is almost entirely due to the lack of resolution among the terminal Amasa spp., illustrating the paucity of synapomorphic characters in these dubious species. Numbers at nodes indicate Bremer support.