Platystethynium Ogloblin, 1946

Platystethynium Ogloblin, 1946: 290 . Type species: P. onomarchicidum Ogloblin, by original designation.

Platypatasson Ogloblin, 1946: 293 . Type species: Platystethynium fransseni Ogloblin, 1946, by original designation. Synonymy by Donev & Huber, 2002: 118.

Parastethynium Ogloblin, 1964: 106 . Lapsus for Platystethynium .

Pseudocleruchus Donev & Huber, 2002: 118 . Type species: Pseudocleruchus triclavatus Donev & Huber, 2002, by original designation. Synonymy by Ortis et al., 2020: 10.

Diagnosis. FEMALE. Females are distinguished from all other genera by the following combination: head strongly triangular (Fig. 8); mandibles short, without teeth, and with a distinct gap between them (Fig. 2b); pronotum longitudinally divided medially (Fig. 4); mesosoma dorsoventrally flattened (Fig. 9); fore wing with venation at most 0.33× fore wing length.

Remarks. Platystethynium, represented in New Zealand by one species of the subgenus Platypatasson, is the first new genus reported for the country since the genera were keyed by Noyes & Valentine (1989). In their key, females would key to Apoxypteron, at the first half of their couplet 67. Males key to couplet 9 but do not fit either half. Among other features, Platystethynium (Platypatasson) differs from Apoxypteron by the longitudinally divided pronotum (pronotum not divided in Apoxypteron), the short and relatively wide parastigma (Fig. 5) (parastigma long and uniformly thin in Apoxypteron), and the venation about 0.3× fore wing length (venation 0.4× fore wing length in Apoxypteron).