Apoprionospio Foster 1969

Genus Apoprionospio Foster, 1969

Type species: Apoprionospio dayi Foster, 1969, by original designation.

Diagnosis (after Blake et al. 2020, amended): Prostomium subtriangular or wedge-shaped, broad anteriorly, often with medial peak, caruncle extending to end of anterior margin of chaetiger 1; 2–3 pairs of eyes or absent; occipital tentacle lacking. Peristomium reduced, free, or fused with the first chaetiger, surrounding prostomium posteriorly as a collar; lateral wings absent; one pair of densely ciliated palps on frontal surface, palp sheaths absent. Notopodial lamellae of anterior chaetigers lateral rather than dorso-medial. Notopodial prechaetal lamellae very large in anterior chaetigers, basally fused with notopodial postchaetal lamellae, forming a V-shaped cup; the cup does not extend to distal tip of lamella. Dorsal crest or folds on chaetiger 7 present or absent. Neuropodial lamellae enlarged on chaetiger 2. Branchiae from chaetiger 2, numbering four pairs, with pairs 1–3 apinnate triangular or cirriform, pair 4 with flattened, plate-like pinnules. Anterior chaetae all capillaries; multidentate hooded hooks present in posterior noto- and neuropodia; secondary hoods of hooded hooks present or absent; ventral sabre chaetae present. Pygidium with one long dorsomedial cirrus and two shorter ventrolateral lobes.

Remarks: Imajima (1989) described Apoprionospio dayi japonica as a new subspecies from Japan after comparing his specimens with the description of A. dayi Foster, 1969 described from North Carolina, USA. Imajima (1989) distinguished A. dayi japonica from A. dayi because the former has the peristomium completely separated rather than fused with chaetiger 1, and the neuropodial lamellae on chaetiger 2 is bluntly rounded, rather than extremely large and triangular with the long axis extending ventrally. We propose that these character differences are sufficient to consider the subspecies as a distinct species. Therefore, we propose raising the status of A. dayi japonica Imajima, 1989 to a full species A. japonica.