3306 Hutchings, Pat Capa, María Peart, Rachael Zootaxa 2012 2012-05-09 3306 1 60 3PC7K Hutchings & Capa & Peart, 2012 Hutchings & Capa & Peart 2012 [151,388,1087,1113] Polychaeta Sabellariidae Idanthyrsus Animalia 17 18 Annelida species willora sp. nov.   Figures 1E–F, 6A, 9, 10, Table 1    Material examined.  HOLOTYPE: 1, WAM V7852*,  West Australia: Quondong, 17°34'S 122°09'E,  01.vii.1975, collected beneath intertidal rock slabs, 45 mmin length, 5 mmin width, 48 chaetigers.  PARATYPES: 1, WAM V7853*, 32 mmin length, 5 mmin width, 47 chaetigers, 1, AM W37779 (mounted for SEM on two pins), both paratypesfrom same sample as holotype.   Additional material examined.   Western Australia: Dampier Archipelago Kendrew Isl. 20°28'30"S116°325'12"E  7.v. 1973, 8 m, 1, WAM V3812; transect N, Kendrew Isl. 20°28'28"S 116°25'12"E  11.ii.1973, 1–  2 m, 1 WAM V899; Lady Nova Flat, NE Rosemary Isl.  2.xi.1971, intertidal on oyster, 3, WAM V677; northeast side of Cape Naturaliste, 33°32'S115°00"E,  26.xii.1958, low tide, 2, WAM V855, under stones; Port Denison, 32°10'51"S 115°45'12"E,  27.x.1973, 9.7–10.6 m, 1, WAM V626, on pieces of reef; Near Little Isl.off Sorento, 31°34'36"S115°44.22"E,  vi. 1974, 3 m on bivalve shells, 1, WAM V3820; Cottesloe Reef, 32°35'39"S115°58.29"E,  14.vi.1973, intertidal on  Ninellamollusc, 3, WAM V313.   Northern Territory: Trepang Bay, 11°13'S 131°57'E,  15.x. 1981, 5 m, 1, NTM W26*, from edge of reef.    Description. Holotyperobust, compact ( Fig. 1E), with dark pigment patches throughout ventrum, on abdominal tori and caudas. Operculum partially fused lobes ( Figs 9A, B, 10F), with an outer row of 17 pairs of paleae, with cylindrical and smooth shafts, flat and curved blades, with sharp-tipped denticles present on anterior half of shaft ( Fig. 10C), length of which declines towards to tip, more splayed basally ( Figs 1F, 9A, 10C). Inner row with 13 pairs of cylindrical paleae, slender, smooth, tapering gently with slightly curved tips ( Fig. 10C, D). Opercular papillae, 12 pairs, inserted externally to outer paleae on each lobe ( Fig. 1E). Four pairs of nuchal spines (hooks) on each side ( Figs 1F, 9A), long shafted, and cylindrical, with subacute tips, lacking limbation; longest ones with more rounded tips, weakly recurved ( Figs 1E, F, 9D, 10B). Tentacular filaments compound, arranged in 20 transverse, long rows ( Fig. 9A, B). Small median organ present at dorsal juncture of opercular lobes ( Figs 1F, 9A, 10A). Eyespots along sides of median ridge. Palps tapered, about one third length of opercular lobes. Segment 1 (chaetiger 1) with lobe-shaped neuropodia ( Fig. 9C), with thin and flattened capillary neurochaetae, with serrations on their margins, decreasing in size towards fine tips ( Fig. 10E). Segment 2 (chaetiger 2) with four pairs of large triangular-shaped lobes, connecting branchiae to neuropodia ( Figs 1F, 9B, C). Neuropodia of chaetiger 1 and 2 not vertically aligned, those of chaetiger 2 situated more laterally ( Fig. 9C), neurochaetae similar in structure. Fourty-five pairs of dorsal branchiae present from chaetiger 2, wide based ( Fig. 9C), not meeting mid dorsally, continuing along entire length of body, but diminishing in size posteriorly so by posterior segments very small ( Figs 1E, 9E). Segments 3–5 (parathoracic) with two typesof notochaetae arranged in two rows, 11 lanceolate slightly curved forming a shallow scoop with slightly twisted frayed tips and blades and 11 short, thinner lanceolate chaetae inserted between each of larger ones ( Fig. 10F). Segments 3–5, with lanceolate neurochaetae arranged in two tiers and significantly different in width, largest ones with smooth blades and smaller ones with textured blades. Parathoracic notochaetae more robust than parathoracic neurochaetae. Abdominal region with 43 chaetigers. Notopodia as transverse tori, with uncini, numbers per torus decreasing posteriorly. Each uncinus with two rows of vertical teeth, each with eight teeth ( Fig. 10H). Neuropodia with capillaries becoming longer posteriorly, with thin, flattened blades ornamented with thecal laminar extensions, distally forming oblique rows with elongate thin tips ( Fig. 10G), similar in structure on all abdominal chaetigers. Cauda smooth about one third the length of abdomen ( Figs 1E, 9E).   FIGURE 9.Photos of  Idanthyrsus willora n. sp.holotype (WAM V7852) A. Anterior end, latero-ventral view. B. Same, laterodorsal view. C. Detail of structures in anterior segments, lateral view. D. Detail of operculum, paleae and nuchal spines. E. Posterior end, lateral view. Abbreviations: b2, branchia segment 2; ca, cauda; cn1, cirrus neuropodia segment 1; chn1, chaetae neuropodium segment 1;ip; inner paleae; ll2, lateral lamellae segment 2; ns, nuchal spines (hooks); mo, median organ; op, outer paleae; tf, tentacular filaments.   FIGURE 10.SEM of  Idanthyrsus willora n. sp.(AM W37779) A. Anterior end ventral view. B. Anterior end dorsal. C. Outer paleae. D. Inner paleae. E. Neurochaeta of segment 1. F. Lanceolate and capillary notochaetae from parathorax. G. Anterior abdominal neurochaetae, in detail. H. Uncini from mid abdominal. Scales A, B = 200 µm, C, D = 100 µm, E, F=30 µm, G = 20 µm, H = 10µm.   Variation.Material examined, including sexually mature females, varies from 10–35 mmin length without cauda, 2–6 mmin width, with 36–48 chaetigers, 14–18 pairs of outer paleae, 8–15 pairs of inner paleae, 8–17 pairs of opercular papillae, 1–4 pairs of nuchal hooks, 12–20 rows of compound tentacular filaments and 29–45 pairs of dorsal branchiae. These variations can be mainly attributed to size of the specimens, with larger animals tending to have more paleae, papillae, tentacular filaments and dorsal branchiae than smaller ones.    Remarks.  Idanthyrsus willorais described as a new species because of the presence of four pairs of lateral lobes on segment two, which have irregular margins. The number of lateral lobes is a feature only shared with  I. saxicavus( Baird, 1863)although in the latter species these lobes are long and digitiform ( Kirtley 1994: Fig. 6.15.1). These two species are also distinguished by the shape of outer paleae increasing in size slightly towards tips in the new species, while in  I. saxicavusthey are similar in size all along the paleae.  Idanthyrsus willora n. sp., can be distinguished from the other Australian species by several features.  Idanthyrsus willorahas straight denticles increasing in length towards the tip on the outer paleae while there are curved denticles similar in length along the blade in  I. australiensis.The number and shape of lateral lobes on segment 2 also varies, (four large triangular ones in  I. willora n. sp., two poorly developed in  I. nesos n. sp., and three triangular ones in  I. australiensis).  Idanthyrsus willora n. sp., also differs from  I. nesos n. sp., in having branchiae continuing to the far posterior segments.  Idanthyrsus willora n. sp., can be separated from other species recorded from the Indo-Pacific by the absence of branchiae on posterior segments, whereas they are present in  L. boninensis Nishi & Kirtley, 1999, described from Japan. Another Japanese species,  I. okudai Kirtley, 1994, can be separated from  I. willora n. sp., based on the number of pairs of lobes on segment 2 (four in  I. willora n. sp., and only two in  I. okudai). Two other species from from Sri Lanka,  I. kornickeri Kirtley, 1994and  I. bicornis( Schmarda 1861), both poorly described (see Table 1), are distinguished from  I. willora n. sp., in the shape and arrangement of the denticles on the outer opercular paleae which are curved and similar in length along the blade in  I. kornickeri, in contrast to those from  I. willora n. sp., which are straight and increase in length towards the tip.  Idanthyrsus bicornishas these denticles arranged opposite to each other along the shaft, and in  I. willorathey are arranged in an alternate pattern on both margins. More over, the nuchal hooks in  I. bicornisare limbate whereas they are not in  I. willora n.sp.    Distribution. Western Australiaand Northern Territory.   Habitat.Specimens found in the intertidal but there is no information available as to whether this species is gregarious or occurs as single individuals, since specimens examined had all been removed from their tubes. Some of the records indicate they were attached to mollusc shells.    Etymology.The specific name  willorais the Aboriginal word for the typelocality Quondong ( Endacott 1973). 1975-07-01 WAM Australia -17.566668 West 1278 122.15 Quondong 17 18 V7852 1 holotype WAM, AM Australia 17 18 V7853 1 paratype W37779 AM Australia 17 18 2 paratype 1958-12-26 1974-06 1958-12-26 WAM Sorento Dampier Archipelago Kendrew Isl. 2 -31.576668 Near Little Isl. 20 115.753334 Port Denison 17 18 V3812, V899, V677, V855, V626, V3820, V313 1 Western Australia 1981-10-15 NTM -11.216666 Trepang Bay 1295 131.95 17 18 W26 1 Northern Territory