Sclerocoelus mandibulum Kuwahara, Marshall & Paiero, 2025, sp. nov.
Creators: name: Kuwahara, Gregory K.
name: Marshall, Stephen A.
name: Paiero, Steven M.
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Diptera
Sphaeroceridae
Sclerocoelus
Sclerocoelus mandibulum

description: Sclerocoelus mandibulum sp. nov.
urn:lsid:zoobank.org:act: 624EB012-8E65-42D5-A039-FF8A9 CAD 323F
Figs 7H, 84–86
Etymology
This name refers to the male postgonite which, in lateral view, strongly resembles the mandible of a rodent (from the Latin ‘ mandibulum ’, meaning ‘jaw’).
Material examined
Holotype
ECUADOR • ♂; Pichincha, Cotopaxi National Park, Quebrada Mishahuaycu; 3600 m a.s.l.; 26 Oct.–8 Nov. 1999; S.A. Marshall leg.; along stream, pan traps; QCAZ debu00139611.
Paratypes
BOLIVIA – La Paz • 1 ♂; Mapac, Lago Titicaca; 16°10′ S, 69°5′ W; 23 Apr. 1997; L. Masner leg.; CBFC.
ECUADOR – Carchi • 1 ♂; Cerro Pelado; 3200 m a.s.l.; 25 Jun. 1965; L.E. Peña leg.; CNCI • 1 ♂; Páramo, 14.1 km NW of El Angel; 3450 m a.s.l.; 1 Nov. 1999; S.A. Marshall leg.; under Polylepis litter; DEBU • 1 ♂; Troya; 2950 m a.s.l.; 11–13 Jun. 1965; L.E. Peña leg.; CNCI. – Napo • 3 ♂♂; near Lago Papallacta; 6 Nov. 1999; S.A. Marshall leg.; under tree branches (brown leaves); QCAZ. – Pichincha • 20 ♂♂, 5 ♀♀; same data as for holotype; DEBU • 21 ♂♂, 5 ♀♀; same data as for holotype; QCAZ.
Description
BODY (Fig. 84A). Length 3.1–4.1 mm. Head dark brown, lower fifth of frons orange; face and gena brown; pedicel brown, postpedicel orange. Frontal width 2.2× frontal height. Three pairs of interfrontal bristles, middle pair largest; anterior orbital 0.5× length of posterior. Palpus brown. Eye large, greatest height about 3.5× shortest genal height. Thorax brown, scutum with paler lateral edges. Two pairs of dorsocentral bristles (anterior pair distinct, 0.5× length of posterior pair) separated by 6–7 rows of acrostichal setulae. Membrane around prosternum bare. Legs brown, hind tibia darker. Fore femur with four large ventral preapical setae. Dorsal surface of male mid tibia with a strong seta about midlength and a pair of large setae at about four-fifths; dorsal surface of female mid tibia with standard chaetotaxy. Ventral surface of male mid tibia with two rows of stout setae in apical third. Wing (Fig. 7H) slightly infuscate. CS2 subequal to CS3. Halter brown.
MALE ABDOMEN (Figs 84B–C, 85). Dark brown, posterior edges of tergites sometimes slightly desclerotized. T2–5 and S2–4 uniformly long-setose with large posterolateral setae. S5 rectangular, 1.0× length and 1.3× width of S4, posterolaterally long-setose and posteromedially emarginate with a broad, dark, rectangular, anteriorly setulose lobe projecting dorsally (into abdomen), emargination with long setae along margin. Anterior flange of S6+7 triangular, 1.0 × as long as wide. Sclerite A not differentiated from S6+7; sclerite B reduced, pale, arched; sclerite C dark, well sclerotized and projecting ventrally off of S6+7; sclerites D and E fused, quadrate with a pale, deflexed left lobe; sclerite F large, thick and flattened with an elongate, angulate apicoventral process on left side; sclerite G very large, rounded, inflated, ring sclerite incorporated into right posterior margin. Epandrium very large, 0.8× length of S8, height 1.6× maximum length and 0.9× maximum width, densely setose, cleft between inner ventral corner and surstylus, and ventral margin projecting ventrally; perianal pads weakly developed. Pseudocercus undifferentiated; halves of subepandrial sclerite very thin, strongly arched, and narrowly contiguous. Subcercus large, with a ventrally bilobed, rectangular posterior part, a broad, rounded inner lobe extending to near anterodorsal corner of surstylus, and a long, dorsally curved, blade-like lobe originating from inner lobe. Hypandrium with thick, dorsoventrally flattened anteromedial apodeme. Surstylus large, curved inwards, somewhat T-shaped with a rectangular, preapical posterior lobe and a triangular apical anteroventral lobe. Postgonite stout, gradually tapered, and apically curved anteriorly. Phallapodeme very large, dorsoventrally flattened; basiphallus dorsoventrally flattened near base, with a large, tapered epiphallus, distal part of basiphallus extending posteroventrally; distiphallus short, largely membranous with a pair of S-shaped ventrolateral sclerites and a V-shaped ventral sclerite.
FEMALE ABDOMEN (Fig. 86). T7 broad, simple; T8 divided into a small, pale, dorsal sclerite and two large, dark, lateral sclerites, posterolateral corners rounded. Epiproct pentagonal, posteromedially cleft (almost entirely divided), and entirely setulose. Cercus large, elongate, with large apical, dorsal, and apicoventral setae. S7 broad, broadly desclerotized posteriorly with six large posterior setae; S8 broad, medially pale with dark lateral edges bent ventrolaterally. Two spermathecae, bulb elongate, bean-shaped, finely striate with a wide, deep invagination on thicker end.
Distribution
Neotropical: Bolivia, Ecuador.
Remarks
Sclerocoelus mandibulum sp. nov. is an unusual species, with an elaborate subcercus superficially similar to the S. regularis group. However, the subcercus is fused to the epandrium and there is no trace of a pseudocercus. Sclerocoelus mandibulum also resembles S. penai sp. nov., another alpine species, in having a large subcercus with a strong inner lobe and a dark, microsetulose process posterior to the posteromedial setulose patch of the male S5, but it is distinguished by the larger size, hammer-shaped surstylus, and uniquely-shaped postgonite. It cannot be confidently placed in any of the named species groups.
description: Published as part of Kuwahara, Gregory K., Marshall, Stephen A. & Paiero, Steven M., 2025, A revision of the genus Sclerocoelus Marshall (Diptera: Sphaeroceridae), pp. 1-277 in European Journal of Taxonomy 979 on pages 76-77, DOI: 10.5852/ejt.2025.979.2803, http://zenodo.org/record/14980852