Proteroscelio, BRUES, 1937

Johnson, Norman F., Musetti, Luciana & Masner, Lubomír, 2008, The Cretaceous Scelionid Genus Proteroscelio Brues (Hymenoptera: Platygastroidea), American Museum Novitates 3603 (1), pp. 1-8 : 2-3

PROTEROSCELIO BRUES

Proteroscelio Brues , in Carpenter et al., 1937: 39. Original description. Type: Proteroscelio antennalis Brues , by monotypy and original designation. Walker, 1934: pl. 1, fig. 2; Muesebeck and Walkley, 1956: 392, citation of type species; Carpenter, 1992: 471, diagnosis; Johnson, 1992: 467, catalog of species.

DESCRIPTION: Body length 1.1–1.7 mm, gracile, mesosoma dorsoventrally depressed, head anteroposteriorly compressed.

Head wider than long, strongly transverse when viewed dorsally; vertex rounded, hyperoccipital carina absent; occipital carina absent; lateral ocellus distinctly separated from inner orbit by distance greater than one ocellar diameter; compound eye large, apparently bare. frons flat, without frontal depression, median longitudinal carina absent; no interantennal prominence visible; submedian carina absent; orbital carina absent; lower frons without fanlike striae; width of interocular space very broad, distinctly greater than eye height; clypeal region, mouthparts not clearly visible; antenna 14-merous; radicle inserted apically into base of A1, more or less parallel to longitudinal axis of A1; apical antennomeres forming a clava, either laterally compressed or generally enlarged; claval formula at least A7–A14/1–2–2–2–2–2–2–1.

Mesosoma strongly depressed; pronotum in dorsal view campanulate, ecarinate; netrion present as a narrow fusiform sclerite, closed ventrally; anterior margin of mesoscutum meeting pronotum dorsally; mesoscutum semioval in outline; notauli absent; parapsidal lines not distinguishable; skaphion absent; transscutal articulation well developed; scutellum semicircular, unarmed, flattened; mesopleuron strongly inclined anteriorly; mesopleural depression broad, deep; mesopleural carina absent; details of sculpture of meso-, metapleural area obscured; legs elongate, slender; femora weakly incrassate; trochantellus present on all legs; outer surface of tibiae without visible spines; tibial spur formula 1–2– 2, spurs on mid- and hind tibiae fine, short; tarsal formula 5–5–5; tarsomeres tapering in width apically, cylindrical; pretarsal claws simple; forewing extending nearly to apex of metasoma; R slightly, but distinctly bent at origin of basal vein, extending through basal 0.6 of length of forewing, without large bristles; costal cell basad of confluence of R with margin slightly darkened, more densely setose, R at this point more lightly pigmented, perhaps representing a bulla; r–rs nearly perpendicular with costal margin; R 1 continuing short distance along costal margin to form postmarginal vein; hind wing with R tracheate throughout its length, complete, i.e., reaching hamuli and costal margin; no strong bristles on R; three hamuli present; length of posterior marginal cilia of hind wing about one half greatest width of wing.

Metasoma weakly to strongly depressed, distinctly longer than head and mesosoma combined; segments subequal in length, T2 slightly longest; seven terga and sterna visible externally; laterotergites slightly widened, sharply flexed over lateral margin of metasoma, no submarginal ridge visible on sterna; T1 with basal carinate margin; S1 with median longitudinal ridge, apparently not protruding anteriorly between hind coxae; anterior margin of S2 straight; felt fields on sterna lacking; cerci visible as fingerlike appendages; apex of gonoplac visible protruding from metasoma.

DIAGNOSIS: This genus is distinguished from others with 14-merous antennae, i.e., Nixonia and Archaeoscelio , by the strongly flattened head and mesosoma, and the seven visible terga and sterna in the metasoma, and the well-developed stigmal (r–rs) and postmarginal (R 1) veins.

COMMENTS: In view of the age of these fossil species, it is reasonable to ask whether Proteroscelio is, in fact, a member of the family Scelionidae . The superfamily Platygastroidea has been defined on the basis of two characters: the presence of basiconic gustatory sensilla on the apical antennomeres, and the hydrostatic ovipositor system ( Austin et al., 2005). The latter system cannot be observed in the fossil material, but the sensilla are clearly visible on the antennae of both species. These structures seem to be unique to the Platygastroidea . Within the superfamily, the family Platygastridae is defined by a series of reductional character states, none of which are found in Proteroscelio . Scelionidae have no defining synapomorphies and the family is probably paraphyletic, i.e., it is synonymous with the concept of the superfamily minus the Platygastridae . Thus, by default, Proteroscelio falls within the family Scelionidae . At least on the basis of the limited available material and our current understanding of the phylogeny of platygastroids, we see no compelling reason to propose any new family-group taxa.