Magelonidae

Taylor, Abbie, Mortimer, Kate & Jimi, Naoto, 2022, Unearthing the diversity of Japanese Magelona (Annelida: Magelonidae); three species new to science, and a redescription of Magelona japonica, Zootaxa 5196 (4), pp. 451-491 : 481-482

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)

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)