Spiophanes japonicum Imajima, 1991

Prostomium blunt, anteriorly truncate or rounded, anterior margin with entire anterior margin. Lateral horns present. Caruncle present. Occipital antenna present (cirriform). Nuchal organ long, extending back more than one segment, extending posteriorly to chaetiger 10–12. Eyes present, or absent; 2 eyes. Palps simple, lacking basal sheath. Dorsal ridge connecting bases of branchiae on chaetiger 1 absent. Prominent dorsal collar on setiger 2 absent. Dorsal branchiae absent. First branchiae without process at base on anterior face. Accessory branchiae arising from posterior part of notopodium absent. Ventral branchiae absent. Chaetiger 3 without filament at base of branchiae. Dorsal crests present; first dorsal crest present on chaetiger 18. Ventral crests absent. Chaetiger 1 notopodium present. Chaetiger 1 notochaetae present. Neuropodial lobe of chaetiger 2 rounded, approximately symmetrical. Neuropodial lobes of posterior chaetigers a single lobe. Interparapodial pouches absent. Chaetigers 2–4 similar, not strongly differentiated. Chaetiger 5 unmodified, similar to subsequent chaetigers. Posterior modified notochaetae absent. Notopodial hooded hooks absent. Neurochaetae of chaetiger 1 include stout hooks. Neuropodial hooded hooks present, first present on chaetiger 14. Neuropodial hooded hooks with accessory tooth or teeth above the main fang, 3 accessory teeth (quadridentate). Shaft of neuropodial hooded hooks of constant thickness, lacking a constriction. Neuropodial sabre chaetae present, in ventral-most positions, first on chaetiger(s) 4. Neuropodial spines absent. Embedded bunches of notopodial needle chaetae absent. Reports of bi- or tridentate hooks Spiophanes spp. (eg Blake & Kudenov, 1978) have been shown to describe quadridentate hooks which are worn or have been observed in an inappropriate orientation (see Meissner & Hutchings ms.). Pygidium terminal with 2 dorsolateral anal cirri.

Description generated from: Wilson, RS & McDiarmid, H 2013. Spionidae (Polychaeta)- A DELTA database of genera, and Australian species. Version 2; originally published as In RS Wilson, PA Hutchings & CJ Glasby (eds) Polychaetes: An Interactive Identification Guide. CSIRO Publishing, Melbourne.

Additional references:
Meißner, K and Hutchings, PA. 2003. Spiophanes species (Polychaeta: Spionidae) from Eastern Australia, with a description of new species, new records and an emended generic diagnosis. Records of the Australian Museum 55, 117-140.