Pyriporoides libita Gordon 1989

Pyriporoides libita (Gordon, 1989)

(Fig. 6)

Daisyella libita Gordon, 1989: 1325, figs 3A, B. Pyriporoides libita: Gordon et al. 2009: 289.

Material examined. Holotype: NIWA 998 (H-536), NIC Wellington, Stn F 127, 49°22.0’ S, 176°16.0’ E, 1280 m, NE Campbell Plateau, 28 January 1965. Paratype: NIWA 999 (P-748), same data as for holotype. Other material: NIWA 95602, same data as for holotype; NIWA 95680 (with labelled specimen of P. circularis), Stn T 39, 49.5033° S, 178.7433° E, 995 m, N of Antipodes Island, 14 March 1981; NIWA 23447, NIC Wellington, Stn TAN 0306 /6, 50.9427° S, 164.6092° E, 1105–1140 m, Christable Seamount, W of Auckland Islands, 14 April 2006. TAN 0307 / 79, 49.8105° S, 175.3216° W, 887–908 m, W of Bollons Seamount, 2 May 2003.

Redescription. Colony comprising encrusting uniserial runners, zooids having a cruciform budding pattern with a lateral daughter zooid produced more or less at right angles from a pore-chamber on either side of the widest point of the zooidal dilatation (or budding is suppressed); no other lateral pore-chambers; total colony spread c. 14 mm. Autozooids elongate-pyriform–claviform, with a proximally tapered portion generally one-third total zooid length [ZL 610–905 (774); DL 456–661 (566); CL 106–333 (195); DW 300–389 (328)], the gymnocyst proximally and laterally extensive, sloping to the substratum. Opesia and cryptocystal shelf surrounded by a raised elongateoval cryptocystal rim, often highest proximally, which is minutely tubercular on the edge and inner face [CrL 243– 334 (289); CrW 149–223 (182)]. Proximal cryptocystal shelf about a third of the length of the oval cryptocystal rim, flat, gently sloping towards opesia, narrowing on each side towards opesial constriction, surface smooth. Opesia more or less dumbbell-shaped, constricted midlength by rounded projections that have a tubercular surface; distal (lower edge) and proximal opesial rims gently rounded, the proximal rim sometimes obliquely so [OpL 121– 169 (152)]. Operculum flap-like, occupying area of opesia distal to constriction. Articulated spines pericryptocystal, 8–13 in total, the distal 4–6 spines more or less erect, the remainder slightly curved toward or over the opesia; spine bases tending to indent cryptocystal rim laterally and proximally. No additional spines borne on the gymnocyst. Ooecium a little wider than long, smooth-surfaced, with only a thin median suture line, its opening not closed by zooidal operculum [OoL 221–234 (227); OoW 187–222 (208)]. Ooecial kenozooid projecting beyond ooecium, with a frontal perforation surrounded by an area of granular cryptocyst; occasionally the ooecial kenozooid is transformed as an avicularium, with a relatively large central foramen, no mandibular pivots, and a raised elongate-triangular rostrum with a rounded tip [AvL beyond ooecium 167–223 (195); AvW 123–223 (178)]; a pair of small communication pores typically present on the lateral walls of the heterozooid. Occasional kenozooids, usually triangular, within the linear chains of zooids, typically (but not always) forming as a consequence of a developing zooid unable to complete its growth owing to collision with another zooid; other kenozooids form reparatively within broken autozooids. Ancestrula like later zooids, lacking a cauda.

Remarks. Additional material discovered since the first description of the species led to the discovery of the avicularian heterozooid associated with the ooecium, as well as additional information on the ancestrula, variation in morphological character and size, and geographic distribution.

Distribution. Endemic to the New Zealand EEZ, where it is found only on the extensive subantarctic Campbell Plateau from Christable Seamount (isolated just to the west of the plateau), northeastwards to the area north of Antipodes Island, including the saddle between Pukaki Rise and Bounty Plateau, at depths of 887–1750 m on hard substrata such as metamorphic rock (Christable Seamount) and, more usually, vesicular basalt [all other localities mentioned by Gordon (1989)].