Prionospio thalanji Wilson & Humphreys, 2001

Prostomium blunt, anteriorly truncate or rounded, anterior margin with entire anterior margin. Lateral horns absent. Caruncle present, continuing back to chaetiger 1, free from dorsum. Occipital antenna absent. Nuchal organ short, at most one segment long. Eyes present; 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 present, first present on chaetiger 2. Dorsal branchiae absent from many median and posterior chaetigers, last present on chaetiger 30. Dorsal branchiae continuous. Dorsal branchiae free and separate from notopodial lamellae throughout, all simple. First branchiae without process at base on anterior face. Dorsal branchiae longest on anterior-most chaetigers, decreasing posteriorly. Dorsal branchiae of anterior-most chaetigers are about 2 times as long as notopodial lobe, branchiae reducing in absolute and relative size posteriorly so that by chaetiger 25 branchiae and notopodia are about equal in length. All branchiae simple (lacking pinnae) but with ciliated margins. Accessory branchiae arising from posterior part of notopodium absent. Ventral branchiae absent. Chaetiger 3 without filament at base of branchiae. Dorsal crests absent (but anterior 22 chaetigers with a single transverse ciliated band across the dorsum of each segment). 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 simple capillaries similar to those of subsequent chaetigers. Neuropodial hooded hooks present, first present on chaetiger 60–65. Neuropodial hooded hooks with accessory tooth or teeth above the main fang, multiple accessory teeth (more than 3) (6 accessory teeth in 2 rows of 3), secondary tooth closely applied to the main fang, about 45º. Shaft of neuropodial hooded hooks of constant thickness, lacking a constriction. Neuropodial sabre chaetae absent. Neuropodial spines absent. Embedded bunches of notopodial needle chaetae absent. The hooded hooks are minute and were not observed until viewed with SEM; the hood is closely applied to the head of the hooded hook and no accessory teeth were visible using SEM. Subsequently, neuropodia from chaetigers 68 and 69 were removed from the SEM mount and a permanent light microscopy slide was prepared and figured (fig ...). Pygidium with a pair of lateral lappets and a vestigial median ventral cirrus (observed prior to mounting specimen but no longer visible in SEM preparation).

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:
Wilson, RS & Humphreys, WF 2001. Prionospio thalanji sp. nov. (Polychaeta: Spionidae) from an anchialine cave, Cape Range, north-west Western Australia. Records of the Western Australian Museum Supplement 64, 105-113.