Crenulister, Caterino, Michael S. & Tishechkin, Alexey K., 2014

Caterino, Michael S. & Tishechkin, Alexey K., 2014, New genera and species of Neotropical Exosternini (Coleoptera, Histeridae), ZooKeys 381, pp. 11-78 : 42-46

Crenulister gen. n.

Type species.

Crenulister grossus sp. n.

Description.

Size range: Length 1.7-3.2 mm; width 1.5-2.8 mm; Body: body rather broadly ovoid, variably subdepressed to rather strongly depressed, rufescent to rufopiceous. Head: frons broad, frontal corners rounded, rather prominent over antennal bases; frontal disk depressed in common with epistoma, frontal stria recurved dorsad within depression, usually complete; sides of epistoma variably ridged, carinate and/or striate; labrum broad, apical margin generally carinate, truncate to weakly emarginate; mandibles with small or no basal teeth on incisor edge; submentum flat to slightly depressed, sparsely setose; mentum about half as long as wide, arcuately narrowed anteriorly, apical margin acutely emarginate; cardo smooth and glabrous, stipes with few setae along lateral margin; ultimate palpomeres fusiform; antennal scape elongate, curved, weakly carinate along anterior margin; funicle weakly widened beyond 5th antennomere, 8th antennomere slightly shorter than preceding; antennal club elongate, widest just beyond midpoint, tomentose, with interrupted basal annulus near midpoint and complete annulus between midpoint and apex, slightly enlarged basad at middle, particularly on dorsal surface. Pronotum: pronotal sides weakly arcuate, convergent to anterior corners, slightly to distinctly explanate at sides, marginal stria usually complete along lateral and apical margins, submarginal stria present very close to sides, absent across front, weakly crenulate; pronotum with pair of gland openings very close to anterior margin behind eye and glands variably displaced posterad onto pronotal disk, usually multiplied along a visible track bearing up to 5 distinct openings along its length; pronotal disk with secondary punctures, when present, strongly concentrated across basal half. Elytra: elytral disk weakly to moderately convex, all striae coarsely impressed, each stria comprising two alternating series of interconnected punctures, appearing chain-like at their most dense; epipleuron usually with one complete marginal stria, with fragments of a second in posterior half or not, inner subhumeral stria usually complete, dorsal striae 1-4 complete, 5th and sutural striae rarely obsolete basally, bases of 4th or 5th and sutural striae rarely connected by weak basal arch; ground punctation of elytral disk fine to coarse, with at least a few coarse secondary punctures usually present in most interstriae. Prosternum: prosternal keel generally distinctly, subacutely emarginate at base, with complete carinal striae usually united in narrow anterior arch, short secondary lateral strioles frequently present between carinal striae and procoxae; lateral prosternal striae present, divergent in front of coxae; prosternal lobe one-half to two-thirds length of keel, apically rounded to subtruncate, with marginal stria present at middle, variably obsolete at sides. Mesoventrite: mesoventrite subacutely produced at middle, with complete marginal stria smooth to crenulate; mesometaventral stria crenulate, usually strongly arched to angulate anterad onto middle of mesoventral disk, disk frequently with sparse secondary punctures. Metaventrite: metaventral disk with coarse secondary punctures usually over most of surface, postmesocoxal stria present, recurved anterad to mesepimeron or ending freely posterolaterad coxa, lateral metaventral stria sinuate, extending from inner corner of mesocoxa toward middle of metacoxa, frequently abbreviated apically; coarse punctures of metepisternum may coalesce into vague to distinct striae. Abdomen: ventrites mostly coarsely punctate, punctures tending to coalesce into striae along apical margins of ventrites 2-4; 1st ventrite with poorly developed lateral stria along inner edge of metacoxa, abbreviated or curving laterad behind coxa; propygidium transverse, 2-3 × as wide as long, with single gland opening on each side, often borne on weak convexity behind anterolateral corner, sometimes associated with weak oblique striole, disk generally sparsely covered with shallow secondary punctures, punctures often sparser in apical half; pygidium more or less equilateral, apex rounded to weakly subacute, gland openings generally present near lateral margin one-fifth to one-fourth from base, these often associated with lateral marginal pygidial striae; marginal stria when present rarely complete around apex; pygidial disk variably punctate. Legs: all trochanters bearing single long seta; profemur rather dilated at middle, narrowed, slightly emarginate at inner apex, protibia generally rounded, strongly spinose, tibial margin only rarely emarginate between to form marginal teeth; protibial spurs present but generally weak; protarsus of both sexes with strongly spatulate setae; meso- and metafemora weakly dilated basad middle, with complete posterior marginal stria; meso- and metatibiae similar, weakly widened to apex, with series of long, rather thin marginal spines; meso- and metatarsi with 4 ventral spines along apical margins only. Male genitalia: accessory sclerites vestigial or absent; T8 with sides evenly tapered to subtruncate apex, basal membrane attachment line generally tangential to deep, rounded basal emargination, ventrolateral apodemes produced most strongly at base, narrowed apically, separated by about one-third T8 width beneath; S8 short along midline, with longer divergent lateral guides bearing several strong setae along apicoventral margin, with weak membraneous velum across entire apex; T9 with ventrolateral apodemes not strongly tapered, inner apices subquadrate beneath, T9 apices subacute to obliquely subtruncate; T10 entire, may be emarginate basally and/or apically; S9 rather short, with broad truncate to emarginate base, head variably subquadrate, apically emarginate, with apical flanges separate; aedeagus rather broad, flattened, sides rounded, apical division conspicuous, apices often distinctly separate, medioventral process strong, produced beneath near midpoint; basal piece one-fourth to one-third tegmen length, with distinct medioventral tooth; median lobe short, proximal arms strongly narrowed basally. Female genitalia: T8 forming single broad plate; S8 forming separate median and lateral plates, basal baculi thin, narrowly attached to lateral sclerites, convergent proximally; S9 slightly elongate, articulated with strap-shaped extension from apex of S8; T10 weakly sclerotized; valvifers paddle-shaped, paddles rather short, about one-third valvifer length; coxites 2.5 –3× as long as wide, tridentate, with weak inner tooth, prominent median tooth, and intermediate lateral tooth; gonostyle nearly as long as median tooth, setose; bursa copulatrix membranous, lacking sclerites, weakly expanded; spermatheca weakly sclerotized, globose, borne on long thin stalk inserted at base of common oviduct, with elongate, spiraled spermathecal gland attached near its midpoint.

Diagnosis.

In most respects this genus is highly distinctive. However, many of the distinguishing characters vary considerably within the group, in addition to appearing in unrelated species, and it is only through a combination of external characters and male genitalia can an unambiguous diagnosis be provided. For most species, the pattern of pronotal punctation, with coarse punctures restricted to the basal half of the pronotal disk (Figs 18A, 19A, C, 22A, 23A), is distinctive, and this in combination with coarsely impressed elytral striae (Fig. 18C) and sparse secondary punctures in the elytral interstriae will separate most species. The longitudinal tracks of multiplied pronotal gland openings (Fig. 19G) are also very unusual, and will put most species here easily. If the above are true, and the protarsi have spatulate setae, the diagnosis is unambiguous. Finally, the male genitalia of Crenulister also exhibit several distinctive characteristics, in particular the rather broad, flat aedeagus, with strong, acute ventromedial process (see Fig. 20E), frequently with the tegmen apices separated, the few strong setae at the apex of the 8th sternite (Fig. 20B), and the broad, medially subquadrate ventrolateral apodeme of the 9th tergite (Fig. 20C). A single (undescribed) species in a distantly related group shares all of these external characters, and represents an amazingly similar overall body form. The only good characters to distinguish it are its lack of spatulate protarsal setae, and its entirely different male genitalia, with its aedeagus strongly narrowed and hooked apically, completely unlike the short, broad and flattened aedeagus of Crenulister .

Phylogenetically, Crenulister emerges from within a diverse group of mostly undescribed taxa that we loosely term the 'scutellar impression group’, particularly a small subgroup related to the named species Phelister blairi Hinton.

Etymology.

The genus name refers to the ubiquitously crenulate elytral striae found in the species of this genus, in conjunction with the common histerid ending -ister. The gender of the genus is masculine.

Key to species of Crenulister