Acanthocystidae Claus 1874, emend. Cavalier-Smith and von der Heyden 2007
Periplast with two or three types of siliceous scales, a basal layer of typically oval plate scales (usually without an inrolled hollow edge; only exception Raphidocystis) and an outer layer of radial funnel-shaped siliceous spine scales and/or radial needle-like scales sometimes apically branched and/or with a peltate radially symmetrical basal disc lacking a lateral indentation (unlike Choanocystis radial scales).
1. Acanthocystis Carter 1863
Periplast with two types of endogenous silicious elements: tangential base plates and nail shaped radial spicules. Spicules with a cylindrical shaft attached to the central part of a radially symmetrical base-plate.
Acanthocystis turfacea Carter 1863
Acanthocystis penardi Wailes 1925
Acanthocystis myriospina Penard 1890, emend. Dürrschmidt 1983
Acanthocystis pectinata Penard 1889, emend. Siemensma & Roijackers 1988
2. Raphidocystis Archer 1867
Periplast with three types of siliceous elements: elliptical or sub-rectangular tangential plate scales with a broad hollow marginal rim. The external surface can be reticular or smooth. Straight tube- or trumpet-shaped radial spine scales (spicules). Smaller funnel-shaped radial spine scales (spicules).
Raphidocystis tubifera Penard 1904
3. Pseudoraphidocystis Mikrjukov 1997
Periplast with two types of siliceous elements: tangential plate scales without a hollow marginal rim and radial funnel-shaped spine scales without an axial rod (shaft, sternum).
Pseudoraphidocystis flabellata (Dürrschmidt 1987) Mikrjukov 1997
Pseudoraphidocystis glutinosa (Penard 1904) Mikrjukov 1997