Polychaeta
Systematics and identification

—Systematics
Overviews of the systematics of the pelagic polychaeta are given by Greeff (1876), Bergström (1914), Fauvel (1916), Wesenberg-Lund (1935, 1939), Støp-Bowitz (1948), Dales (1957), Day (1967), Uschakov (1972), Rice (1987), and Pleijel and Dales (1991). Uschakov (1972) suggested that the pelagic families, despite their biological differences and external morphologies could be placed in the suborder Phyllodociformia using the name proposed by Levinsen in 1882 without systematic rank. This suborder belongs to the order Phyllodocemorpha (Livanov, 1940, fide Uschakov, 1972), which includes the marine polychaetes with the most primitive characters. Pleijel and Dales (1991) have considered that holoplanktonic families of uncertain phylogenetic affinities belong to the superfamilies Phyllodocoidea (Alciopidae, Lopadorhynchidae and Pontodoridae), Iospiloidea, Typhloscolecoidea and Tomopteroidea in the order Phyllodocida.
Fauchald (1974) reviewed the morphological and anatomical features used in the taxonomy of recent polychaetes, and discussed some principles of their phylogeny. He proposed that the evolution of the different polychaete families was a rapid radiation from several ancestors adapted to life in the semi-consolidated detritus layer above the sea bottom. Støp-Bowitz (1984) has discussed the systematic problems in the families Alciopidae, Tomopteridae and Typhloscolecidae. Pleijel (1991) suggested that holoplanktonic families are derived from benthic phyllodocid polychaetes. The systematic study of some of these families are included in major works, such as Greeff (1876), Bergström (1914), Uschakov (1972), and Pleijel and Dales (1991).
Eight families of holoplanktonic polychaetes have been recorded from the South Atlantic Ocean. Pontodora pelagica has not yet been recorded in this region, and it belongs to a monogeneric and monospecific family, Pontodoridae. The phylogenetically isolated polychaete Poeobius meseres has only been found in the North Pacific Ocean.

Order Phyllodocida
Family Alciopidae
Family Iospilidae
Family Lopadorhynchidae
Family Pontodoridae
Family Tomopteridae
Family Typhloscolecidae
Family Yndolaciidae
Order Fauvelopsida Fauchald, 1977
Family Flotidae Buzhinskaya 1996

—Identification
There is no complete top-down key available. First, by comparing diagnostic characters of the eight planktonic polychaete families, the family must be established. Then, at Page 10: Polychaeta the section starts with separate family keys.