(Edwards, 1929)
Body
Small larvae up to 3 mm long, with a straight transportable case that hardly, if at all, widens near the apex Stempellinella case. Posterior parapods with simpel claws only (Brundin, 1948; Wiederholm, 1983).
Head
The S3 is bifid Stempellina S3 bifid9.
Antenna
The antenna stands on a tall pedestal with a simpel large apical projection and consists of 5 segments. The blade is longer than the flagellum. Segment 2 with alternate large basal and distal Lauterborn organs. The basal pedicel is short and the distal pedicel is long and reaches beyond the flagellum Stempellinella brevis ant.
Mentum
The mentum has a rounded median tooth and 6 pairs of lateral teeth Stempellinella mentum 2. The ventromental plates are widely separated and about as wide as the mentum
Labrum
SI is a comb and labral lamellae a single plate with numerous apical teeth. The pecten epipharyngis consists of 3 long slender triangular scales. The premandible has 2-3 apical teeth Stempellinella labrum pm pe.
Mandible
The mandible with a dorsal tooth, apical tooth and 3 inner teeth. The pecten mandibularis is present and seta interna with branches.
Differential characteristics
Of all Tanytarsini only Stempellinella and Zavrelia have alternate Lauterborn organs Stempellinella alternate LO. Stempellinella can be separated from Zavrelia by the shorter antennal blade, reaching only slightly beyond the antenna Stempellinella ant both while in Zavrelia the blade reaches far beyond the antenna Zavrelia antenna. Also a premandible with 2-3 apical teeth and a blunt inner tooth Stempellinella labrum pm pe (4 sharp apical teeth in Zavrelia Zavrelia labrum pe premand) and the pecten epipharyngis with 3 long slender scales (3 very small scales in Zavrelia) is distinctive.
S. brevis can be separated from S. minor by the short distal pedicel of the lauterborn organ and the bifid S3.