Appendicularia
Taxonomy

Fol (1872) proposed one of first classification schemes for appendicularians, dividing the group (a family according to his classification) into two subfamilies depending on the presence/absence of endostyle and heart. One of the subfamilies encompassed the genera provided with both structures (Oikopleura and Fritillaria), and the other a single genus without them (Kowalevskia). Lohmann (1896), presented another scheme, subsequently modified (Lohmann, 1933), that established the basis of the classification most widely accepted today. He divided the class Copelata into two families: Fritillaridae and Oikopleuridae, the latter with two subfamilies: Oikopleurinae and Bathochordaeinae. Subsequently, most authors (e.g., Fenaux, 1967; Bückmann and Kapp, 1975) have recognized a third family, Kowalevskiidae, with a single genus, Kowalevskia.

Tokioka (1957), described a new genus of Oikopleuridae, subfamily Oikopleurinae, from the Pacific Ocean: Sinisteroffia, but Bückmann (1970) suggested that the diagnostic characteristics of the specimens studied by Tokioka, may have been fixation artifacts. Recently, Fenaux and Youngbluth (1990) described a new genus, Mesochordaeus, of the subfamily Bathochordaeinae, on the basis of a single specimen collected at mesopelagic depth in Bahamian waters. Subsequently, Fenaux and Youngbluth (1991) and Fenaux (1993) described three new genera of Oikopleurinae (Inopinata, Mesopelagica and Mesoikopleura), also on the basis of mesopelagic specimens from the North Atlantic Ocean and the Mediterranean Sea. These last records raised the number of species known previously to 64, of which 43 have been recorded in the South Atlantic Ocean.