Anokkostenostomum anatirostrum (Marcus, 1945) comb. nov. (Fig. 4A) Stenostomum anatirostrum Marcus, 1945 Stenostomum bryophilum Luther, 1960 Description: Adult specimens 0.2–0.75 mm long. Chains with two zooids (0.5–1 mm) or six zooids (2.5 mm). Anterior end generally rounded, spatulate or sharply arched with ‘anatiform’ aspect. Constriction before the pharynx. Posterior end rounded. The intestine reaches the caudal body region. Epithelium with short uniform cilia and rigid sensory cilia scattered on the body surface, more numerous in the anterior region. Rhabdites regularly distributed in the adult specimens; but in immature individuals only visible in the ciliated pits. Lateral and broad ciliated pits. Colour in life whitish. Anterior brain lobes formed by small independent masses (‘metamerics’). No light-refracting bodies. Oral pore oval, frequently surrounded by radial or longitudinal muscular bundles. Pharynx 1.5–2 times longer than it is wide. Presence of conspicuous transverse muscular bundles. Elongated pharyngeal glands (type b) placed on both sides of the pharynx, grouped in clusters and opening into a simple duct. Immature individuals without pharyngeal glands. Presence of excretophores. Protonephridium slightly sinuous, nephridiopore terminal. Distribution: São Paulo, Brazil (Marcus, 1945b); Tvaerminne, Finland (Luther, 1960); Sabakoekreek, Surinam (Van der Land, 1970); Cheshire and Yorkshire, England; near Poznan, Poland, and south of Mombasa, Kenya (Kolasa & Young, 1974a); France (Lanfranchi & Papi, 1978); Fosso Contesora, Italy (Kolasa, 1983); south-eastern New York State, USA (Kolasa et al., 1987; Kolasa, 1991).

Published as part of Noreña, Carolina, Damborenea, Cristina & Brusa, Francisco, 2005, A taxonomic revision of South American species of the genus Stenostomum O. Schmidt (Platyhelminthes: Catenulida) based on morphological characters, pp. 37-58 in Zoological Journal of the Linnean Society 144 (1) on page 50, DOI: 10.1111/j.1096-3642.2005.00157.x, http://zenodo.org/record/4634680