Sclerostomus Burmeister, 1847

Grossi, Paschoal C., 2009, Generic limits in South American stag beetles: taxa currently misplaced in Sclerostomus Burmeister (Coleoptera: Lucanidae: Lucaninae: Sclerostomini), Zootaxa 2139, pp. 23-42 : 25-27

Genus Sclerostomus Burmeister, 1847

(subgenus Sclerostomus )

Sclerostomus Burmeister 1847: 423 . Replacement name for Sclerognathus [ Westwood], 1845. Type species Sclerognathus costatus [ Westwood], 1845. The type species of a replacement genus is the same as that of the previously established genus (Article 67.8, ICZN 2000).

Sclerognathus [ Westwood] 1845: 27. Junior homonym of Sclerognathus Valenciennes, 1844 (Pisces) . Type species Sclerognathus costatus [ Westwood], 1845 by monotypy.

Hemicardanus Heller 1927: 213 . Synonym of Sclerostomus . Type species Hemicardanus interruptocarinulatus Heller, 1927 by original designation.

Sclerostominus Weinreich 1960: 85, as subgenus. Type species Sclerostomus trunctatus Lüderwaldt, 1935 by original designation. New synonymy.

Description. Lucanidae : Lucaninae : Sclerostomini. Length: 11.0–14.5 mm. Width: 4.0–5.0 mm. Sexually dimorphic. Head: Form enlarged, transverse, wider than one elytron width, greater in males. Disc roundly excavated, less in females. Surface punctate; punctures fine to coarse, disc of females with large punctures. Sides of anterior margin prominent and rounded. Supra antennal prominence distinct, round to conically shaped, sometimes forward directed. Ocular canthi well developed, externally projected in males, rounded in females. Temporal process present or not in males, absent in females; if present, process small, conical, never exceeding canthus width. Labrum trapezoidal, somewhat vertically positioned, with a conical discal process; in females larger and directed forward. Mentum transverse, lateral margins rounded, anterior and posterior margins parallel (males), female with concave anterior margin; surface totally punctate; punctures moderate to coarse, sometimes coalescent. Mandibles in males symmetrical, as long as or longer than head, apex always bifurcate (males) with dorsal lobe rounded or truncate, directed upwards; dorsal margin of males with an almost horizontal internal tooth, sometimes removed from dorsum to internal edge of mandible; ventral internal margin with a flattened process; ventral surface always with a row of setae; setae erect, confined to a longitudinal or polygonal excavation. Mandibles of females asymmetrical, shorter than head; incurved, with acute apex; left mandible with a stronger internal bifid tooth; right mandible with a smaller tooth, sometimes obsolete; dorsal surface with longitudinal carina; ventral surface glabrous. Antennal club mostly glabrous with only distal surface of each antennomere tomentose and with few scattered setae. Pronotum: Shape subquadrate, sometimes transverse, anteriorly convergent with sinuous sides. Anterior angles acute to truncate; posterior angles acute to rounded. Lateral margins crenulate with some dispersed setae. Dorsal surface generally with a longitudinal rhomboid furrow at midline with a microrugose surface, opaque, moderately punctate; punctures moderate to large. Furrow sometimes just indicated as a weak longitudinal line with fine punctures. Each side laterally with two circular shallow punctate fovea; punctures fine to coarse. Anterior margin at middle projected in medium sized and major males; projection conical or flattened dorsally and weakly bifurcate at apex, never reaching above middle of head. Elytra: Shape elongate, weakly convex, longer than both head and pronotal length together. Surface serially punctate; punctures moderate to coarse, basally moderately dense. Some species with longitudinal shining elevated carinae; carinae continuous or interrupted. Humeri rounded, with or without a sharply curved callus. Elytral declivity without carina and with setose coarse punctures; elytra laterally with or without scattered short setae (scales lacking). Wings: Fully developed. Legs: Protibiae totally dentate externally from base to apex; teeth increasing in size distally; scarcely to moderately covered by short to long yellow setae, especially on external side. Mesotibiae and metatibiae with a strong external tooth near middle, with 0–3 smaller teeth above. Apex of metatibiae acute in males and truncate or dentate in females. Ven t er: Mesosternum at middle flat, not convex or projected. Male genitalia: Genital capsule complex, with additional lobes or projections. Dorsal plate (Fig. 1a) convex, subquadrate; integument hard, sclerotized with some clear areas; somewhat membranous. Posterior margin bifid or incised; laterally with an elongate posterior lobe and/or bulbous protuberance, sometimes absent or weakly indicated. Ventral plate (Fig. 1b) subtriangularly shaped, anteriorly narrow, elongated; posteriorly wide with or without a trapezoid projection above a membranous plate, setose; setae restricted to basal edge of projection or near posterior margin. Aedeagus strongly sclerotized (Figs. 3a–c); everted internal sac constricted distally with spiculae at base, middle, or apex (Fig. 3b).

Distribution. Brazil, Argentina, and Paraguay.

Diagnosis. The combination of the following characters distinguish Sclerostomus from other genera of Lucanidae : Pronotum in both sexes with rhomboid midline furrow and with 2 depressed fovea on each side. Elytral vestiture apparently glabrous with single setae in each puncture and sometimes with scattered setae laterally. Mandibular shape of males with an internal dorsal tooth, apex always bifurcate and with a rounded or truncate dorsal lobe, ventral surface of mandibles with a row of setae. Elytra with shining carinae in some species, or irregularly punctate. Male genitalia with complex, strongly sclerotized genital capsule and a concentrated row of setae on the parameres.

Remarks. Four species are currently included in this subgenus, all from the Atlantic coast of Brazil, with their distributions sometimes extending into some more continental areas of Brazil, Argentina, and Paraguay. In Brazil, they are distributed in the Atlantic Forest and some transitional areas of the Cerrado and Caatinga ecoregions, and are always found at elevations above 500 m in wet or dry forests. The northeasternmost known record is of S. delislei , described from southern Bahia and recently collected near the Bahia border in Minas Gerais. This species seems to have the most restricted distribution. In contrast, S. sulcicollis is widely distributed in southeastern Brazil, and S. costatus and S. truncatus are distributed throughout the southern Brazilian states and northern Argentina, with S. truncatus also occurring in Paraguay (Puerto Bertoni, Alto Paraná, and Capitán Miranda, Itapúa, new country record).

Almost nothing is known about the biology of Sclerostomus , except all species have been collected at light traps, indicating nocturnal behavior. Three species, S. costatus , S. sulcicollis , and S. truncatus have also been collected inside small logs of about 10–20 cm in diameter.