Subfamily Cenocimbicinae n. subfam.

http://zoobank.org/ urn:lsid:zoobank.org:act: FA885793-D7D8-49A8-A00D-6C813ACBFC0F

Type genus. Cenocimbex Nel, 2004.

Diagnosis. Distinguished from all other Cimbicidae by forewing with 2r-m distinctly curved, meeting M distal of 2m-cu; cell 2r+pterostigma distinctly higher than cell 3r; and a combination of the following: eyes converging ventrally; antenna with 7–9 antennomeres, club 3-segmented; mesonotum with median longitudinal mesonotal sulcus and notauli distinct; metanotum short, with cenchri oval; tibial spur acute, long; first abdominal tergite with hind margin straight or weakly emarginated.

Remarks. Cenocimbicinae differ from individual subfamilies of Cimbicidae by: from all by 2r-m as in diagnosis; from Abiinae, Cimbicinae by eyes converging ventrally [Cimbicinae: more or less parallel; Abiinae: converging dorsally], by at least one tibial spur acute, long (equal length of first tarsomere, one known, see F-774, tentative Leptostigma brevilatum) [Abiinae, Cimbicinae: blunt]; from Corynidinae, Pachylostictinae by 2r-m posterior insertion distal to cell 2mcu [Corynidinae, Pachylostictinae: proximal to], by cell 2r+pterostigma distinctly higher than cell 3r [not so], antenna with more than five antennomeres [five], club 3-segmented [non-segmented], metanotum short [long]; further from Corynidinae by mesonotum with median longitudinal mesonotal sulcus and notauli distinct [reduced or absent]; from some Abiinae and Cimbicinae by cenchri oval, from some Cimbicinae also by first abdominal tergite with hind margin straight or weakly emarginated [deeply emarginated].

Attribution of the Cenocimbicinae to the Tenthredinoidea is confident by 1-M meeting R and 2r-rs meeting Rs distally to 2r-m, and to the Cimbicidae by their clubbed antenna, and a unique forewing venation characteristic of the core cimbicid subfamilies Cimbicinae and Abiinae and found nowhere else in Hymenoptera: venation complete for Hymenoptera (except Sc, Rs between Rs+M and 1r-rs, and Rs bifurcation lost), characteristically narrow (low) cell 3r, and 2r-m crossvein meets M distal to 2m-cu.

The long, curved to strongly curved crossvein 2r-m is distinct, occurring only rarely in extant Cimbicidae (very few Abiinae, cf. Vilhelmsen 2019, Fig. 16A; and Cimbicinae, cf. Vilhelmsen 2019, Fig. 16B) and in the Miocene of China (Abiinae: cf. Zhang et al. 1994, Fig. 121; Cimbicinae: cf. Zhang et al. 1994, Fig. 118), which we consider convergent.

The new subfamily comprises the oldest known Cimbicidae, from the Selandian of Menat and less than ten million years later in the Ypresian Okanagan Highlands deposits of far-western North America (Archibald et al. 2011), a rather narrow interval of time but across a great distance of the Holarctic.

Genera included. The type genus, Allenbycimbex n. gen. and Leptostigma n. gen.

Locality and age. Menat, France, Selandian; Okanagan Highlands (McAbee,Allenby Formation, and Republic), far-western North America, Ypresian.