Trifionychidae Lepeco & Melo, 2022

Lepeco, Anderson, Barbosa, Diego N. & Melo, Gabriel A. R., 2022, A remarkable new family of stinging wasps from the Cretaceous of Myanmar and China (Hymenoptera, Aculeata), Journal of Hymenoptera Research 94, pp. 163-190 : 163

† Trifionychidae Lepeco & Melo fam. nov.

Type genus.

† Trifionyx Lepeco & Melo, gen. nov.

Included genera.

† Prionaspidion Lepeco & Melo, gen. nov., † Trifionyx Lepeco & Melo, gen. nov., † Trifionyximus Lepeco & Melo, gen. nov., † Mirabythus Cai, Shih & Ren.

Diagnosis.

The following set of characters differentiate † Trifionychidae fam. nov. from other aculeate lineages: falciform mandible, apex abruptly tapering and becoming strongly curved at distal two-thirds; apex of clypeus widely rounded and projecting over mandibles; frons protruding over lateral portion of clypeus, forming tube in which antennal radicle is inserted; antennal socket directed laterally on head, below ocular level; both sexes with nine flagellomeres; partial or complete fusion of veins C and Sc+R on forewing; and base of the metasoma forming small petiole (more easily visualized in ventral view). Other helpful diagnostic characters found in all family members are the percurrent notauli, strongly diverging anteriorly; dorsal surface of propodeum posteriorly delimited by transverse carina; and third valvula very elongated, undivided, and exposed at rest. Additional features unique to some members of the family are the clypeal apex sometimes with serial indentations, giving it a serrate aspect († Mirabythus , † Prionaspidion gen. nov. and, to a lesser extent, † Trifionyx gen. nov.) and trifid tarsal claws († Trifionyx gen. nov. and † Trifionyximus gen. nov.).

Description.

Head. Large, as wide as or wider than mesosoma; prognathous to obliquely hypognathous. Palps shorter than mandible. Mandible wide basally, with well-delimited depressed region between anterior condyle and posterior acetabulum; distally tapering and curved. Labrum very reduced, inconspicuous. Clypeus large; apex widely rounded and projected over mandibles. Malar space width between one or two times the diameter of scape. Frons protruding over lateral portion of clypeus, forming tube concealing antennal radicle. Compound eye ovoid, bulging. Three ocelli present. Hypostomal bridge long, at least as long as basal mandibular width; anteriorly delimited by strong and curved carina between bases of mandibles. Occipital carina well developed, complete. Antennal socket directed laterally on head, anterior to ocular level; dorsal rim slightly projecting over radicle. Antenna. Scape long, tubular, at least twice as long as its maximum width; main shaft of scape forming angle of about 45° in relation to insertion of radicle. Pedicel long, narrowed at base, at least twice as long as its maximum width. Flagellum with nine flagellomeres. Mesosoma. Pronotum anteriorly declivitous; pronotal flange well developed, covering propleuron in dorsal view; dorsolateral lobe reaching tegula; posterolateral corner narrow, strongly projecting towards procoxa. Propleuron with percurrent carina dorsally; dorsal and ventral edges completely abutting; posterior edges not diverging; epicoxal lobe present. Basisternum small, most of external portion of prosternum facing backwards. Notaulus well developed, indicated as percurrent sulcus; notauli strongly diverging anteriorly. Parapsidial lines absent. Scutellum shorter than mesoscutum; anteriorly with broad and deep sulcus posterior to transscutal articulation; axillae small. Prepectus absent, mesepisternum forming a continuous sclerite. Ventral portion of mesepisternum anteriorly marked by strong transverse angulation; mesocoxal foramina small, separated from each other by more than twice their width. Metanotum short, not covered by scutellum medially. Metepisternum broadly separating metacoxae ventrally, but not forming plate; submetapleural carina well developed above metacoxa. Metacoxal foramen small. Propodeum long, at least as long as mesoscutum; dorsal and posterior surfaces well defined; spiracle positioned on transition between lateral and dorsal portions of the sclerite; propodeal foramen separated from metacoxal foramina by sclerotized bridge. Legs. Coxae small and globose. Femora broad. Protrochanter elongated; inserted posteriorly on procoxa. Meso- and metatrochanters very small, globose. Forewing. Veins C and Sc+R partially fused, costal cell obliterated. With one or no submarginal cell enclosed by tubular veins. Veins 3rs-m and 2m-cu absent. Veins not reaching distal margin of wing. Metasoma. Basally with small petiole; with seven exposed terga and eight exposed sterna on males; less segments exposed on females. T1 small, forming convex, rounded plate; posterior margin entire; lateral line absent. T2-T6 wider than long, posterior margins widely rounded. S1 rounded, relatively reduced; S2-S5 wider than long, posterior margins widely rounded. Without constriction or specialized articulation between first and second metasomal segments. Sting apparatus. Well developed. Seventh sternum enclosing most of sting. Second valvifer very narrow. Third valvula longer than wide, narrow; as a unique piece, without articulation; permanently exposed in some of the taxa. Terebra curving upwards. First and second valvulae of equal size. Furcula well developed, V-shaped, with very short posterior arm.