Type genus. Microrbinia Hartman, 1965. Designated by Blake 2000.
Diagnosis. (Emended). Body small, separation of body into thoracic and abdominal regions weakly defined or lacking; parapodia lateral throughout, not shifted dorsally in abdominal segments. Branchiae present or absent. Prostomium broad, bluntly rounded or more elongate and conical or acute; nuchal organs present. Peristomium with 2–3 achaetous rings, separated from prostomium, sometimes only vaguely defined dorsally, laterally, or ventrally. Noto- and neuropodial postsetal lamellae with short postsetal lobes or absent. Bases of podia separated throughout; setal tori reduced. Setae consisting of capillaries always present, blunt-tipped spines or uncini and swan hooks present or absent; furcate setae typically absent. Pygidium with anal cirri present or absent.
Inclusive genera. Microrbinia, Orbiniella, Proscoloplos, and Pettibonella.
Remarks. Only species of Microrbinia and Orbiniella were identified in this study. Three species of Orbiniella are new to science. Species of Microrbiniinae are in part defined on negative characters.