Sabellaria pyramis, Hutchings & Capa & Peart, 2012

Hutchings, Pat, Capa, María & Peart, Rachael, 2012, 3306, Zootaxa 3306, pp. 1-60 : 47-48

Sabellaria pyramis n. sp.

Fig. 6A, 26, Table 4

Material examined. Holotype: NTM W 10045, 6 mm long, 1 mm wide, posteriorly incomplete with 17 chaetigers, paratypes: 1 NTM W023787 , 10 mm long, 1 mm wide, complete with 28 chaetigers, plus cauda, operculum incomplete; 1, NTM W 10044, 8 mm long, 1 mm wide, incomplete. All type material from Northern Territory: Darwin Harbour , Holotype and NTM W023787 from St. D 24A, 12°25.05'S 130°48.58'E, 8 m, 7.i.1993 and NTM W10044, from St D 98A, 12°31.9'S 130°50.43'E, 18 m, coll 14.vii.1993 .

Description. Holotype pale yellow with scattered brown pigmentation on dorsum of last parathoracic segments and at base of tentacular filaments. Operculum longer than wide, with completely separated lobes. Paleae arranged in three semicircular concentric rows; outer row with 18 pairs, clear and golden paleae with broad flattened smooth blade, distally serrated with fine extended midline plume (majority broken). Middle row with one kind of paleae, five pairs, stout, robust, shaft forming a four sided pyramid with blunt tips ( Fig. 26D). Inner row with nine, geniculate with symmetrical blunt tips directed inwards paleae. Middle paleae longest, outer paleae cover bases of middle, inner shortest. Opercular papillae 12 pairs, shorter than wide, cylindrical ( Fig. 26B). Nuchal spines not observed. Tentacular filaments compound, long, arranged in five transverse rows ( Fig. 26A). Median organ and median ridge present, with eye spots on both margins. Segment 1 (chaetiger 1) with one pair of elongate neuropodial cirri, with long capillaries ( Fig. 26G). Segment 2 (chaetiger 2) with one pair of lateral lobes connecting branchiae to neuropodia ( Fig. 26H). Neurochaetae similar on both segments. Six pairs of branchiae, elongate, strongly ridged, narrow based, tapering to fine tip, not meeting mid dorsally. Segments 3–5 (parathoracic) with two types of notochaetae arranged transversely, eight lanceolate chaetae with fine capillaries imbetween. Segments 3–5 with two types of neurochaetae, 3–4 lanceolate and capillaries imbetween. Abdomen of 23 segments with short neuropodia with capillary chaetae and expanded rectangular notopodia with terminal transverse torus with long handled uncini with 6–8 teeth arranged vertically, similar throughout abdomen. Cauda smooth and equal in length to last ten segments.

Variations. The two paratypes vary in the number of pairs of middle paleae (4–5), inner paleae (9–10) and branchiae (5–6) present, and both are incomplete posteriorly and the opercular lobes are slightly damaged.

Remarks. Sabellaria pyramis n. sp., differs from other species of the genus in the particular pyramidal shape of the middle paleae, unique in the genus. All other described species of Sabellaria have geniculate middle paleae. Even though the genus Sabellaria was not recovered as mophyletic in Capa et al. (2012) or the present study ( Fig. 28C) we have positioned this species within this genus since it shares the combination of features of the rest of the species (operculum completely divided in two symmetrical lobes, inner paleae arranged in two rows, with mid and inner paleae, and three parathoracic segments) together with the shape of outer paleae provided with a distal plume and denticles on both sides.

Distribution. Darwin Harbour, Northern Territory, known only from type locality.

Habitat. Muddy sediments in depths of 8–18 m.

Etymology. The specific name of pyramis refers to the pyramidal shape of the middle paleae.