Composition
This subfamily includes three fossil genera: Siveterella Kornicker & Sohn 2000 with two species in the Palaeozoic, Triadogigantocypris Monostori 1991 with five species in the Mesozoic, and Triadocypris Weitschat 1983 a with three species in the Mesozoic and one in the Permian. Eight additional genera are extant: Actinoseta Kornicker 1958, Asteropella Poulsen 1965, Asteropteron Skogsberg 1920, Asteropterygion Kornicker 1981, Pteromeniscus Kornicker 1981, Omegasterope Kornicker 1981, Microasteropteron Poulsen 1965, and Microasteropteron Kornicker 1994.
Diagnosis
Carapace generally oval in lateral view, but some with small posterior projection at midheight; ventral margin of rostrum and anterior margin of valve below rostrum forming angle either slightly greater or less than right angle; incisure not forming indentation in part of valve just ventral to junction with proximal end of ventral edge of rostrum.
Range
Permian to Holocene.
Remarks
Three species studied herein that had been incorrectly referred previously to either Monopia Claus 1873 or Cypridina MilneEdwards 1840 are referred to Triadocypris or Triadogigantocypris.