Aonides gracilis Tauber, 1879: 115.
Levinsenia gracilis.— Hartley 1981: 146; Gaston 1984: 2.51–2.53, fig. 2.52; Blake 1996: 33 –34, fig. 2.1; Hartmann-Schröder 1996: 386, fig. 183; Kirkegaard 1996: 28 –29, fig. 10; Aguirrezabalaga 2012: 241 –244, figs. 106–107.
Paraonis (Paraonis) gracilis.— Pettibone 1963: 301 –302, fig. 79 a–d.
Paraonis gracilis.— Eliason 1920: 55 –56, fig. 16; Hartman 1957; 330–331, pl. 44, figs 4–5; 1969: 74–75, figs 1–3.
Paraonis (Paraonides) gracilis.— Monro 1930: 150 –152, fig. 58.
Paraonis gracilis gracilis.— Day 1967: 566, fig. 24.4a–b.
Tauberia gracilis.— Strelzov 1973: 127 –133, figs 54–57.
Material examined. ZISP 2 /38028; Barents Sea; 69.8250°N- 46.1833°E; 77 m; 24.08.1959; one specimen (labelled as Tauberia multibranchiata). 2876 Finnmark 593; 70.0860°N – 29.0608°E; 161 m; 13.09.2003; one specimen. 3940 Askeladd Beta SA–02; 71.4750°N – 20.4476°E; 278 m; 26.06.2007; one specimen. 3940 Askeladd Beta SA–09; 71.4778°N – 20.4462°E; 274 m; 27.06.2007; one specimen. 5390 G7122/7-1; 71.05°N-22.05°E; 340 m; 08.09.2015; three specimens. 5390 E7122/4-1; 71.05°N-22.05°E; 340 m; 10.09.2015; three specimens.
Diagnosis. Antenna and secondary ciliary organs absent. Five to six prebranchial segments. Branchiae arranged in 10–15 pairs; about four times as long as wide. Modified notochaetae absent. Modified neurochaetae as long, gently curved hooks bearing a ridge on the convex edge.
Distribution. Eastern Atlantic, from Greenland (Strelzov 1973) to Portugal (Gil & Sardà 1999), including Northern Norway (Oug 2000) and several locations of the North Sea close to Norway (Hartley 1981). Barents Sea (Bilyard & Carey 1980). Western Atlantic from Western Greenland (Blake & Dean 1973) and New England (Pettibone 1963) to Caribbean (Díaz-Díaz et al. 2009) and Uruguay (Strelzov 1973). Mediterranean (Laubier & Ramos 1974). Eastern Pacific, from Oregon (Fauchald & Hancock 1981) to Panama (Aguado & López 2003); Japan (Imajima 1997). Arctic, from Jan Mayen (Bakken et al. 2010) to the Chukchi Sea (Strelzov 1973) and Canadian Arctic (Stewart et al. 1985). Antarctic (Sicinski 2004). Southern Africa (Day 1967).