Thienemann and Bause, 1913
Body
Small larvae up to 5 mm long. The posterior parapods bear about 15 simpel claws. On the basal part of the posterior parapods a stout lateral seta Rheotanytarsus anal segment. The basal part of the case is glued tot the surface of solid substrates and contains about 4-5 ribs that are flaring out distally and support the filtering net Rheotanytarsus case (Walshe, 1950; Wiederholm, 1983).
Head
The S3 is simpel.
Antenna
The antenna stands on a tall smooth pedestal and consists of 5 segments. The basal segment is much longer than the flagellum. Segment 2 is slightly wedge-shaped and longer than the remaining segments. The small Lauterborn organs distally on segment 2 with a pedestal that is longer than segment 3 Rheotanytarsus antenna.
Mentum
The mentum has a notched median tooth and 5 pairs of lateral teeth. The ventromental plates are close together medially and wider than the mentum. When highly focussed, the plates are covered with alternating high and low longitudinal bands suggesting very coarse striae Rheotan mentum small.
Labrum
SI is a comb and labral lamellae a single plate with numerous apical teeth. The pecten epipharyngis consists of 1 smooth plates with about 10-20 distal teeth Rheotan pecten epipharyngis. The plate may tend to be separated into 3 toothed plates. The premandible has 2 apical teeth Rheotanytarsus premandible.
Mandible
The mandible with a dorsal tooth, apical tooth and 2-3 inner teeth Rheotanytarsus mandible. The pecten mandibularis is present and seta interna with branches.
Differential characteristics
The case is distinctive Rheotanytarsus case . Also the pecten epipharyngis with a single comb with 10-20 sharp distal teeth Rheotan pecten epipharyngis is unique in Tanytarsini, but may be hard to see. If the pecten epipharyngis appears to have 3 plates, Rheotanytarsus can be separated from Cladotanytarsus and Neozavrelia by the small Lauterborn organs, not much wider than the pedestals that are as long as or longer than the third segment.
Diversity
European species: 9
Treated species: 0