Unearthing the diversity of Japanese Magelona (Annelida: Magelonidae); three species new to science, and a redescription of Magelona japonica Author Taylor, Abbie Department of Natural Sciences, Amgueddfa Cymru - Museum Wales, Cathays Park, Cardiff CF 10 3 NP, Wales, U. K. & School of Biosciences, Cardiff University, Cardiff CF 10 3 AX, Wales, U. K. Author Mortimer, Kate 0000-0002-3430-1659 Department of Natural Sciences, Amgueddfa Cymru - Museum Wales, Cathays Park, Cardiff CF 10 3 NP, Wales, U. K. & Katie. Mortimer @ museumwales. ac. uk; https: // orcid. org / 0000 - 0002 - 3430 - 1659 ortimer@museumwales.ac.uk Author Jimi, Naoto Sugashima Marine Biological Laboratory, Graduate School of Science, Nagoya University, Toba, Japan & Centre for Marine & Coastal Studies, Universiti Sains Malaysia 11800 USM, Penang, Malaysia text Zootaxa 2022 2022-10-21 5196 4 451 491 journal article 171433 10.11646/zootaxa.5196.4.1 5981d91b-b1c3-4599-b241-58cd7f3937b6 1175-5326 7235610 D11B689F-70DF-4B27-959D-63A520D125E2 Key to adult specimens of known Magelonidae species in the North-Western Pacific ( type localities/ confirmed locations given in brackets (modified from Mortimer et al. 2022 ). Full descriptions of characters can be found in Mortimer et al. (2021a) . 1. Prostomium with distinct prostomial horns................................................................. 2 - Prostomium without prostomial horns, or with a squared anterior margin (often referred to as “rudimentary horns”)....... 9 2. Anterior margin appearing smooth (minute crenulations only present under high magnification)...................... 3 - Anterior margin crenulate (degree of crenulation variable).................................................... 5 3. Deep purple pigment band between chaetigers 5 and 8....................... M. japonica (Korean Archipelago, Japan ) - No marked pigmentation of the thoracic region............................................................. 4 4. Prostomium wider than long, no superior dorsal lobes of the thoracic region. Abdominal parapodia sub-equal, those of the neuropodia being somewhat smaller............................................ M. koreana (Korean Archipelago) - Prostomium longer than wide, superior dorsal lobes from chaetigers 1–8, abdominal parapodia approximately equal.................................................................................. M. boninensis sp. nov. ( Japan ) 5. Prostomium width approximately similar to length.......................................................... 6 - Prostomium wider than long............................................................................ 7 6. Abdominal hooded hooks bidentate......................... M. crenulifrons ( Viet Nam , Hong Kong , Natuna Islands) - Abdominal hooded hooks tridentate................................ M. cf. cornuta ( Hong Kong , Japan , see remarks) 7. Superior dorsal lobes present in the thorax................................................................. 8 - No superior dorsal lobes present in thorax, anterior margin only minutely crenulate............. M. petersenae ( Thailand ) 8. Small superior dorsal lobes present on chaetiger 9, abdominal hooded hooks tridentate.......... M. lenticulata ( Viet Nam ) - No superior dorsal lobes present on chaetiger 9, abdominal hooded hooks bidentate............... M. methae ( Thailand ) 9. Chaetiger 9 with mucronate chaetae..................................................................... 10 - Chaetiger 9 bearing capillary chaetae only, as in chaetigers 1–8................................................ 13 10. Abdominal hooded hooks tridentate..................................................................... 11 - Abdominal hooded hooks bidentate........................................... M. sachalinensis (Sakhalin Island) 11. Anterior thoracic notopodial lamellae with smooth or lightly crenulated upper edges.............................. 12 - Anterior thoracic notopodial lamellae with pectinate upper edges............................. M. pectinata ( Thailand ) 12. Abdominal parapodia without triangular processes at the inner margin of chaetal rows (DML, VML). M. parochilis ( China ) - Notopodial lamellae of chaetiger 8 distinctly bilobed, abdominal parapodia with triangular processes at the inner margin of chaetal rows (DML, VML).............................................................. M. tinae ( Thailand ) 13. Abdominal hooded hooks polydentate............................................ M. agoensis (Ago Bay, Japan ) - Abdominal hooded hooks bi- or tridentate................................................................ 14 14. Thoracic notopodia with superior dorsal lobes............................................................. 15 - Thoracic notopodia without superior dorsal lobes.......................................................... 18 15. Prostomium wider than long........................................................................... 16 - Prostomium longer than wide.......................................................................... 17 16. Thoracic notopodial lamellae slender, no superior dorsal lobe on chaetiger 9..................... M. kamala ( Thailand ) - Stout species, with distinct armour-like appearance, thoracic lamellae foliaceous, superior dorsal lobe on chaetiger 9 present................................................................................. M. armatis sp. nov. ( Japan ) 17. Prostomium only marginally longer than wide, anterior margin squared (very rudimentary horns)..... M. noppi (Thailand) - Prostomium length greater than width, rudimentary horns with a triangular anterior margin....... M. alba sp. nov. (Japan) 18. Anterior thoracic neuropodial lamellae distinctly scoop-shaped........................... M. cf. cincta ( Hong Kong ) - Anterior thoracic neuropodial lamellae slender triangular.................................................... 19 19. Moderate to large species with rudimentary horns, broad palps with several rows of papillae..... M. mickminni ( Thailand ) - Prostomial margin rounded to straight, minute species with slender palps carrying two rows of papillae.................................................................................................. M. pygmaea ( Thailand )