Sclerocoelus argentinensis, Kuwahara & Marshall & Paiero, 2025

Kuwahara, Gregory K., Marshall, Stephen A. & Paiero, Steven M., 2025, A revision of the genus Sclerocoelus Marshall (Diptera: Sphaeroceridae), European Journal of Taxonomy 979, pp. 1-277 : 27-28

Sclerocoelus argentinensis sp. nov.

urn:lsid:zoobank.org:act:2A847776-3A06-4E48-9EF3-3B445DA4475D

Figs 5D , 18–19

Etymology

This name reflects the apparent restriction of this species to Argentina. Four other species of Sclerocoelus are known from the country, but S. argentinensis sp. nov. is the only species known exclusively from Argentina.

Material examined

Holotype

ARGENTINA • ♂; Salta, 22 km N of La Caldera ; 1550 m a.s.l.; 2–30 Dec. 1987; S. and J. Peck leg.; El Ucumar, subtropical humid forest, Malaise trap; DEBU.

Description

BODY ( Fig. 18A ). Length 3.1 mm. Head dark brown, orbital plate, gena and antenna brown. Frontal width 2.3× frontal height. Three pairs of strong interfrontal bristles surmounting a fine fourth pair; anterior orbital 0.4 × length of posterior. Palpus pale brown. Eye large, greatest height about 3.5× shortest genal height. Thorax dark brown, scutum with broad paler lateral edges. Two pairs of dorsocentral bristles (anterior pair only slightly larger than surrounding acrostichal setulae) separated by 5–6 rows of acrostichal setulae. Membrane around prosternum bare. Legs brown, femora basally paler. Fore femur with three large ventral preapical setae. Dorsal surface of mid tibia lacking small posterior seta in basal half. Ventral surface of male mid tibia with two rows of stout setae along apical third. Wing ( Fig. 5D ) slightly infuscate. CS2 0.9× CS3. Halter brown.

MALE ABDOMEN ( Figs 18B–C , 19 ). Dark brown, posterior edges of tergites sometimes slightly desclerotized. T2–5 and S2–4 uniformly long-setose with large posterolateral setae. S5 rectangular, 1.3× length of S4, with a short, dark, asymmetrically boot-shaped, posteromedial area margined anteriorly by long setae and posteriorly by a patch of short, stout setae. Anterior flange of S6+7 small, 1.3× as long as wide. Sclerite A large, posteriorly deeply divided into outer (S7) and inner (S6) parts, inner part densely setulose with a posterior tuft of very dense setulae preceded by a patch of short, stout, tooth-like setae; sclerites B and C absent; sclerite D small, dark, triangular, fused to left side of a small sclerite E; sclerite F large, narrowly fused to sclerite G, setulose except for elongate extension of inner posterolateral corner; sclerite G large, bulbous; ring sclerite well sclerotized. Epandrium small, wedge-shaped, 0.7× length of S8, height 1.4 × maximum length and 0.8× maximum width, posteroventral corner slightly emarginate; anal fissure large, almost circular; perianal pads weakly developed. Pseudocercus absent; halves of subepandrial sclerite reduced. Cercus much larger than surstylus, elongate-rectangular in posterior view, ventral half concave, anteroventral corner slightly flared outwards, posterior surface setulose with a small preapical process. Hypandrium with anteromedial apodeme long and sinuate. Surstylus broad, bulging, anteroventral margin flattened and blade-like, in line with inner surface of basal part with a small tooth-like lobe. Postgonite broad and almost parallel-sided, slightly tapered towards apex, indistinctly sinuate on apical half, apex truncate with a small anterolateral lobe. Phallapodeme long, slightly curved with a large, obliquely ridged dorsal ‘fin’; basiphallus stout and connected to distiphallus by a neck-like distal part; distiphallus only slightly longer than basiphallus, largely membranous with a pair of larger, sinuate, dorsolateral sclerites and a small ventral sclerite.

FEMALE ABDOMEN. Female unknown.

Distribution

Neotropical: Argentina.

Remarks

This distinctive species shows several unusual autapomorphies, such as the prominent posterior tuft of very dense setulae on genital pouch sclerite A. Other characters that help identify Sclerocoelus argentinensis sp. nov. include the very large, posteriorly setulose cerci and stout, tooth-like setal patches on the male S5 and genital pouch sclerite A. Sclerocoelus argentinensis is one of the ‘basal lineages’ of Sclerocoelus , with plesiomorphic states including a complete but narrow subanal plate and cerci not yet differentiated into separate subcerci and pseudocerci. Related species are restricted to high alpine habitats.

Figures

Fig. 5. Sclerocoelus Marshall, 1995, left wings, ventral view. A. Sclerocoelus aduncus sp. nov. B. Sclerocoelus alpinus sp. nov. C. Sclerocoelus altus sp. nov. D. Sclerocoelus argentinensis sp. nov. E. Sclerocoelus azulensis sp. nov. F. Sclerocoelus binus sp. nov. G. Sclerocoelus bucki sp. nov. H. Sclerocoelus caligarius sp. nov. I. Sclerocoelus chilensis sp. nov. J. Sclerocoelus copiosus sp. nov. Scale bars: A–J= 0.5 mm.

Fig. 18. Sclerocoelus argentinensis sp. nov., male holotype (DEBU). A. Male habitus, lateral view. B. Male terminalia, posterior view. C. Male terminalia, lateral view. Abbreviations: cer=cercus; epa= epandrium; ss =surstylus. Scale bars: A=1.0 mm; B–C =0.25 mm.

Fig. 19. Sclerocoelus argentinensis sp. nov., male holotype (DEBU). A. Aedeagus and associated structures, lateral view. B. Male S5 and genital pouch, ventral view. Abbreviations: bp =basiphallus; dp =distiphallus; pg =postgonite; ph =phallapodeme. Scale bars: A=0.20 mm; B=0.25 mm.