Potamethus Chamberlin, 1919

Tovar-Hernandez, Maria Ana & Jirkov, Igor A., 2024, Jasmineira filatovae Levenstein, 1961, the deepest known sabellid is a Potamethus Chamberlin, 1919: redescription, new combination and generic emendation, Zootaxa 5486 (1), pp. 48-70 : 67

Potamethus Chamberlin, 1919 , emended

Diagnosis modified from Knight-Jones (1983), Fitzhugh (1989) and Capa et al. (2019).

Radioles on semicircular lobes, each with at least four rows of vacuolated cells (one species with a single row). Inter-radiolar membrane present or absent, radiolar flanges and basal flanges both absent. Radiolar eyes absent. Dorsal lips with radiolar appendages, pinnular appendages absent; ventral radiolar appendages absent, ventral lips, parallel lamellae and ventral sacs all present, the latter inside radiolar crown. Anterior peristomial ring with narrow ventral lobe. Posterior peristomial ring distinctly elongated, of variable morphology. Moldures in each side of anterior peristomial ring in some species. Peristomial eyespots absent. Thorax usually with eight chaetigers (but some species with 9, 10 or 17 thoracic chaetigers), abdomen with variable number. Glandular ridge on chaetiger 2 present or absent. Ventral shields present. Interramal eyespots absent. Collar chaetae elongate, with narrow or broad hood; inferior thoracic notochaetae paleate. Thoracic uncini avicular, with several rows of progressively shorter teeth above main fang, breast developed or not, medium to long-sized handles, and a small hump on the angle between external margin of neck and handle can be present; neuropodial companion chaetae present, with long handle and distal asymmetrical tip. Abdominal uncini avicular, with several rows of short teeth above main fang, reduced breast, distinctly elongate neck between breast and main fang, elongate handle, and a small hump on the angle between external margin of neck and handle can be present. Abdominal neurochaetae as elongate, narrowly hooded chaetae, in anterior group, and modified, elongate, narrowly hooded chaetae, in posterior group. Pygidial eyespots absent. Pygidial cirrus absent.