[ref. ID; 4356 (Wolfgang Petz and Wilhelm Foissner, 1992)]

Class: Oligotrichea Butschli, 1887
Subclass: I. Halteriia n. subcl.
Order Halteriida n. ord.
Subclass: II. Oligotrichia Butschli, 1887
Order Strombidiida Jankowski, 1980
Order Oligotrichida Butshli, 1887
Suborder Tintinnina Kofoid & Campbell, 1929
Suborder Strobilidiina Jankowski, 1980

Class Oligotrichea Butschli, 1887
Body typically small, ovoid to elongate, Perilemma present in some (all?) species. Somatic ciliature commonly reduced, rarely absent. Adoral zone of membranelles conspicuous, forms flat spiral on peristomial surface ("closed" circle in top view; Strobilidiina, Tintinnina) or extends as cured ribbon onto ventral side ("open" circle; Halteriia, Strombidiida); paroral membrane monostichomonad; no endoral membrane. Morphogenesis enantiotrophic; stomatogenesis apokinetal on or below cell surface; somatic ciliature originates de novo (Halteriia) or by intrakinetal proliferation (Strobilidiina, Tintinnina; uncertain in Strombidiida); macronucleus with one or two replication bands. Mainly planktonic in marine and freshwater habitats.

Subclass Halteriia n. subcl.
Body small, ovoid. Adoral zone of membranelles extends as curved ribbon onto ventral side. Oral primordium develops on cell surface; entire somatic ciliature originates de novo. Predominantly freshwater species, some also edaphic.