Sigalionidae sp. 1 (Neoleanira magellanica (McIntosh, 1885))
Vouchers. TOROA: station 1FB and SEA LION: station 1MFC.
Diagnosis. Both vouchers incomplete, the better preserved voucher (T1FB) 16 mm long, 2 mm wide (including parapodia) for 53 segments. Pharynx not extended. All elytra missing.
Prostomium slightly wider than long, with stout cylindrical ceratophore of median antenna bearing small lateral auricles, style missing; lateral antennae rather short, with distinct ceratophores and ovoid styles. Tentacular parapodium with single aciculum and bundles of extremely long, slender capillary chaetae; tentacular cirri with distinct cirrophores; styles long, tapering, and subequal with dorsal tentacular cirri about 2/3 the length of ventral ones. Eyes absent. Palps long, extending to about segment 15, slender, tapering.
Segment 2 with inflated elytrophores. Segment with pair of short bulbous cirrophores; styles missing. Single digitiform branchia and cuplike ctenidia (3 per parapodium, widely spaced) present from about segment 4, well developed from segment 5. Parapodia distinctly biramous. Notopodia only slightly smaller than neuropodia, long, cylindrical, with circlets of stylodes dorsoposteriorly and terminally, stylodes smooth. Neuropodia long, cylindrical, postchaetal lobe with smooth stylodes. Ventral cirri of 2nd segment inserted basally on neuropodium, longer than in subsequent segments (almost reaching tip of neuropodium); on other segments inserted medially, short, subulate, tapered. Ventral ctenidia not observed in 53 chaetigers.
Notochaetae numerous of 3 types: 1. short, thin capillaries; 2. Short to long slender, finely spinous chaetae; 3. long, more robust, chaetae with wider blade, coarsely serrated on one side. Neurochaetae all spinigers, with smooth stems, blades with alternating spines on both side, distally tapering into long slender tips; blades variable in length.
Original remarks (see also updated remarks). Voucher specimens lack elytra, therefore their generic assignment cannot be confirmed with certainty. But combination of median antenna with auricles, presence of branchiae and spinigerous neurochaetae suggest it may belong to genus Neoleanira Pettibone, 1970. Neoleanira magellanica (McIntosh, 1885) is a species known from the region (type locality: Tierra del Fuego), but Falkland Islands' specimens are small and not all characters can be established with certainty. At present we assign these to morphospecies Sigalionidae sp. 1.
Updated remarks. Following the intial examination on which description above is based, a better specimens (large, with elytra intact) became avalable. It was confirmed that elytra is transluscent to milky, with entire smooth margin and surface and clavate ventral ctenidia are present from mid body onwards. Falkland Islands specimens agree well with Neoleanira magellanica (McIntosh, 1885) and are therefore re-assigned to this species.