Chaetognatha
Outline classification

Phylum Chaetognatha (Leuckart, 1894)
Class Sagittoidea Claus and Grobben, 1905
Subclass Syngonata Casanova, 1985
Order Biphragmophora Casanova, 1985
Family Heterokrohniidae Casanova, 1985
Genus Heterokrohnia Ritter-Záhony, 1911
Genus Archeterokrohnia Casanova, 1986
Genus Xenokrohnia Casanova, 1993
Subclass Chorismogonata Casanova, 1985
Order Monophragmophora Casanova, 1985
Family Spadellidae Tokioka, 1965
Genus Spadella Langerhans, 1880
Genus Paraspadella Salvini-Plawen, 1986 (sensu Bowman and Bieri, 1990)
Genus Hemispadella Casanova, 1996
Family Eukrohniidae Tokioka, 1965 (emend.)
Genus Eukrohnia Ritter-Záhony, 1909
Genus Bathyspadella Tokioka, 1939
Order Aphragmophora Tokioka, 1965
Family Sagittidae Claus and Grobben, 1905
Genus Sagitta Quoy and Gaimard, 1827
Family Pterosagittidae Tokioka, 1965
Genus Pterosagitta Costa, 1869
Family Krohnittidae Tokioka, 1965
Genus Krohnitta Ritter-Záhony, 1910

The genera Krohnittella Germain and Joubin, 1912; Bathybelos Owre, 1973; and Pterokrohnia Srinivasan 1986 need further description in order to be classified in the order Aphragmophora of the system outlined above, although Bieri (1991) created a family for each of them. Bathyspadella, known from a single specimen, was placed in the Eukrohniidae by Tokioka (1965); indeed it has glandular canals, but all other morphologic characters, and its probable benthic habitat, suggest that it may belong in the family Spadellidae.