Type: Rostrocalanus peracutus. Total: 2 spp.

Diagnosis from Markhaseva & al; (2008, p.2421):
Female:
- Cephalosome and 1st pediger fused, 4th and 5th incompletely separate.
- Rostrum large, as rounded plate without filaments.
- Prosome 3.4-5.1 times longer than urosome.
- Posterior corners of prosome prolonged and obtusely rounded or acutely pointed.
- A1 24-segmented.
- A2 coxa without seta; basis with 1 small vestigial seta; endopodal segment 1 with 1 seta; exopod 7-segmented with 0, 3, 1, 1, 1, 0 and 3 setae.
- Gnathobase of Md with keel, cutting edge bearing 4 to 5 teeth, 1 fork-like distally and tipped with 3 to 4 points; endopodal segment 1 without seta, endopodal segment 2 with 6 setae; basis with 2 setae, one very small; exopod 4-segmented with 1, 1, 1 and 1 setae.
- Praecoxal endite of Mx1 with 9 terminal elements, four or five of them as thick spines, other setae modified (with swollen headsà or not; coxal endite with 2 setae, coxal epipodite with 3 to 4 setae, or setae absent; proximal basal endite with 2 setae; distal basal endite fused to endopod, with 5 setae ( setal affiliation obscure); exopod with 5 or 6 setae.
- Proximal praecoxal endite of Mx2 with 1 or 2 setal elements, distal with 3 setae; proximal and distal coxal endites with 3 setae each; proximal basal endite with 4 setae; endopod apparently 3-segmented, with 6 long and slender worm-like sensory setae.
- Syncoxa of Mxp without seta on proximal praecoxal endite, with 1 seta on middle endite and 2 setae on distal praecoxal endite; coxal endite bearing 2 setae. Setae of praecoxal endites poorly sclerotized but not aesthetasc-like; basis with 2 medial setae, distal setae absent; endopod 5-segmented with 3, 2, 2, 3+1, 4 setae.
- P1 basis with or without medial distal seta; lateral lobe of endopod moderately developed.
- P5 uniramous, 2-segmented; distal segment with 3 spine-like unarticulated extensions terminally.

Males unknown.