Magelona

Mortimer, Kate, Cassà, Susanna, Martin, Daniel & Gil, João, 2012, New records and new species of Magelonidae (Polychaeta) from the Arabian Peninsula, with a re-description of Magelona pacifica and a discussion on the magelonid buccal region, Zootaxa 3331, pp. 1-43 : 40-41

Key to adult specimens of Magelona from the western Indian Ocean (revised from Mortimer (2010))

The western Indian Ocean is regarded here as including the seas around the Arabian Peninsula, the seas surrounding east Africa to its southern tip (including Seychelles), and those surrounding Pakistan and western India. The species discussed here are those known to occur in this region. Unconfirmed records have been omitted and confirmed localities are given for each species. Prostomial images are also provided in Figure 13.

1. Prostomium with conspicuous, well-delineated frontal horns.................................................. 2

- Prostomium without horns, or rudimentary horns present..................................................... 7

2. Anterior prostomial margin crenulate.................................................................... 3

- Anterior margin smooth............................................................................... 4

3. Abdominal hooded hooks bidentate, unstained V shape present on venter of mid-thorax, when stained with methyl green (often seen in unstained material)...................................................... M. crenulifrons (Persian Gulf)

- Abdominal hooded hooks tridentate................................................. M. cornuta (Gulf of Oman)

4. Abdominal hooded hooks bidentate, unstained X shape present on venter of mid-thorax when stained with methyl green................................................................................... M. pulchella (Persian Gulf)

- Abdominal hooded hooks tridentate...................................................................... 5

5. Thoracic notopodial lamellae with crenulate upper margins, prostomial horns distinctly separated from prostomium anterior margin, distal horn tips bulbous................................................. M. montera sp. nov. (Red Sea)

- Thoracic notopodial lamellae with smooth upper margins, prostomial horns without bulbous distal tips, horns separated from prostomium anterior margin only at horn tips............................................................... 6

6. Notopodia of chaetiger 9 with subtriangular postchaetal lamellae, with swollen bud-like tips, neuropodia of the same chaetiger with distinctly pointed postchaetal lamellae, and long and slender prechaetal lamellae.......... M. gemmata ( Seychelles)

- Notopodia of chaetiger 9 with digitiform lateral lamellae and broadly rounded triangular postchaetal lamellae; neuropodia with broadly rounded triangular postchaetal lamellae, and short, thick prechaetal lamellae..... M. sinbadi sp. nov. (Persian Gulf)

7. Thoracic notopodia with dorsal processes................................................................. 8

- Thoracic dorsal processes lacking...................................................................... 10

8. Anterior abdomen with lateral pouches, chaetiger 9 with modified chaetae....................................... 9

- No anterior abdominal pouches, chaetiger 9 with capillary chaetae; prostomium onion-shaped with rudimentary horns...................................................................................... M. cepiceps ( Seychelles)

9. Abdominal hooded hooks bidentate; notopodial dorsal processes absent in anterior thorax.................................................................................................. M. conversa ( Seychelles, Persian Gulf)

- Abdominal hooded hooks tridentate; notopodial dorsal processes on all thoracic chaetigers (Note: those of chaetiger 9 may be difficult to discern).......................................... M. obockensis (Gulf of Aden, Red Sea, Persian Gulf)

10. Anterior abdominal chaetigers with greatly enlarged re-curved hooded hooks............................................................................................... M. falcifera ( Seychelles) , M. cf. falcifera (Persian Gulf)

- No enlarged hooks................................................................................... 11

11. Neuropodial lamellae of chaetigers 1–3 expanded distally, scoop-shaped; pigment band present in posterior thorax (Note: pig- ment band may fade)......................................... M. cincta ( South Africa), M. cf. cincta (Persian Gulf)

- Thoracic neuropodial lamellae not distally expanded....................................................... 12

12. Thoracic notopodial postchaetal lamellae larger than neuropodial ones; neuropodial lobes reduce in size in mid-thorax, abdom- inal hooded hooks bidentate................................... M. mahensis Mortimer & Mackie, 2006 ( Seychelles)

- Thoracic postchaetal lamellae in both rami of a similar size and shape, abdominal hooded hooks not bidentate.......... 13

13. Abdominal hooded hooks polydentate (predominately quadridentate).................... M. cf. agoensis (Persian Gulf)

- Abdominal hooded hooks tridentate..................................................................... 14

14. Postchaetal lamellae in thorax and abdomen long, sharply triangular; large, stout species................................................................................................. M. symmetrica ( Seychelles, Persian Gulf)

- Thoracic postchaetal lamellae short, triangular; abdominal lamellae lanceolate, basally constricted; small, slender species.................................................. Magelona pygmaea Nateewathana & Hylleberg, 1991 ( Seychelles)

Figures

FIGURE 13. Prostomia of Arabian Peninsula Magelona species, dorsal views: (A) M. obockensis, 39 chaetiger anterior fragment, proboscis not everted, both palps attached, syntype, MNHN Type 1357; (B) M. obockensis, BMNH: ZB. 1971.54; (C) M. pulchella, holotype, BMNH 1969.391; (D) M. cornuta, holotype, ZMUC-POL- 969; (E) M. montera sp. nov. MNHN A 895; (F) M. sinbadi sp. nov., NMW. Z. 2010.037.0001; (G) M. cf. agoensis, NMW. Z. 2010.037.0004; (H) M. cf. cincta, NMW. Z. 2010.037.0041; (I) M. conversa, BMNH. 2010.234; (J) M. crenulifrons, NMW. Z. 2010.037.0024; (K) M. cf. falcifera, NMW. Z. 2010.037.0010 b; (L) M. symmetrica, NMW. Z. 2010.037.0047 b.