Large larvae, up to 20 mm long. Body brownish. Head capsule rounded-oval; cephalic index 0.9. Dorsally S7 quite ventral relative to dorsal, distant S8 lying near apotome, just posterior to DP; S5 quite anterior, Ventrally VP widely anterolateral to SSm, lateral to S9 which lies just anterior to S10, SSm, S9, S10 forming a narrow trapezoid.
With 5 distinct segments; almost 1/3 longer than mandible. Antennal ratio 7.0. Basal segment about 5x as long as basal width, with ring organ at 0.75; segment 2 about 4x as long as wide; segment 3 about 2x as long as segment 4; segment 4 as long as wide and little shorter than apical segment. Style extending to middle of segment 4. Peg sensilla at most 1/2 as long as style. Blade extending beyond segment 2. Accessory blade 3/4 length of blade.
Robust, strongly curved and considerably broadened distal to apical tooth. Apical tooth long, almost 1/4 length of mandible with short lamella distal to two large, inner teeth. Seta subdentalis 1/2 as long as apical tooth arising from non-extended mola. Ventrolateral setae 1 and 2 short, blunt blades, arising close together in double pit on outer margin; seta 3 multibranched.
Basal segment of palp 3.5 x as long as wide, with ring organ at 0.7.
With fringe of swim-setae. With 4 conical anal tubules, as long as wide. Procercus about 2.5x as long as wide, with about 25 anal setae. Some claws of posterior parapod with large, fine points along inner side, some long; shortest claws curved.
Anatopynia is the only member of the Anatypyniini, and the only genus of Tanypodinae with a true 5-segmented antenna. Although the very large larvae superficially resemble Alotanypus, Macropelopia and Apsectrotanypus, its distinctiveness is evident through all developmental stages. Larvae differ particularly in having multiple rows of teeth on the pecten hypopharyngis, many dorsomental teeth, and a mandible with 2 inner teeth, undeveloped mola, and stumpy ventrolateral setae 1 and 2.
Only one species, A. plumipes, is known with certainty, the larva of which lives in the littoral of small lakes and ponds. This species is recorded in the western Palaearctic from middle to northern Europe: Vallenduuk and Moller-Pillot (2008) discuss the ecology in the Netherlands. Malloch (1934) described A. centralis from Greenland but its status is doubtful since the inadequate description was based to a large extent on colour patterns. Although the name Anatopynia was a wider concept historical (e.g. Edwards, 1931) there are no validated records of the presently-defined genus from outside the Palaearctic.