(Holmgren, 1883)
Body
About 30 anal claws all normal. No tubules on the 10th segment. Anal tubules longer than wide and supra-anal setae are shorter than the anal tubules (Moller Pillot and Goddeeris, 2001).
Head
The S3 is simpel.
Antenna
The antenna stands on a tall pedestal without distal projection and consists of 5 segments. The basal segment is longer than the flagellum. Segment 2 cylindrical and sclerotized for 4/5 of its length Tanyt overig ant pict. Lauterborn organs + pedicel 2 - 2.5 x as long as segments 3 - 5 combined. The base of the pedicel of the lauterborn organs not sclerotized.
Mentum
The mentum has a rounded or notched median tooth and 5 pairs of lateral teeth. The ventromental plates are close together medially and a little wider than the mentum Tatars mentum.
Labrum
SI is a comb and labral lamellae a single plate with numerous apical teeth. The pecten epipharyngis consists of 3 smooth plates with distal teeth.
Mandible
The mandible with 3 dorsal teeth and 2 plates, 1 apical tooth and 3 inner teeth Tanyt gracilentus mand. The pecten mandibularis is present and seta interna with branches (Wiederholm, 1983).
Differential characteristics
Tanytarsini with very long pedestals of the Lauterborn organs Tatars antenna are Corynocera, Krenopsectra, Micropsectra, Parapsectra and Tanytarsus. Corynocera has a distinctive mentum. Krenopsectra, Micropsectra and Parapsectra (unknown in P. uliginosa) have much more than about 15 claws on the posterior parapods and most of the described larvae have an apical spur or projection on the antennal pedestal (only present in T. brundini agg.).
T. gracilentus can be separated from the other Tanytarsus by the 30 claws on the posterior parapods and a mandible with 3 dorsal teeth and 2 dorsal plates Tanyt gracilentus mand. T. gracilentus can be separated from Micropsectra fusca by the dorsal plates on the mandible and no hump on the 11th segment.