Pyriporoides murdochi Gordon & Taylor, 2017, n. sp.

Pyriporoides murdochi n. sp.

(Fig. 8 B–E)

Material examined. Holotype: NIWA 136, NIC Wellington, Stn TAN 0402 /5, 71.7000° S, 172.0300° E, 623 m, ENE of Cape Adare, Antarctica, 4 February 2004. Paratype: NIWA 120, NIC Wellington, Stn TAN 0402 /22, 71.8000° S, 170.9400° E, 151–180 m, N of Cape Adare, Antarctica, 9 February 2004. Other material: Unregistered ancestrula from Stn TAN 0402 /90, 72.2743° S, 171.4640° E, 423 m, S of Cape Adare off Hallett Peninsula, 14 February 2004.

Etymology. Honorific for Dr Robin C. Murdoch, Research Director at the National Institute of Water & Atmospheric Research, Wellington.

Description. Colony comprising encrusting uniserial runners, zooids having a cruciform budding pattern with a lateral daughter zooid produced from either one of the pair of pore-chambers on each side (or lateral budding suppressed); total colony spread c. 11 mm. Autozooids oval to pyriform, with no cauda or a very short one [ZL 532–778 (632); DL 533–623 (581); CL 0–167 (51)], the gymnocyst proximally and laterally extensive, relatively steep-sided. Opesia and cryptocystal shelf surrounded by a raised oval cryptocystal rim that is evenly horizontal and minutely tubercular [CrL 339–389 (354); CrW 221–300 (261)]. Opesia having a longitudinally compressed dumbbell shape, constricted in middle part by rounded to subangular projections that have a smooth or weakly tubercular surface; lower edge of distal opesial rim more or less straight, or weakly convex; proximal opesial rim variable, being gently rounded, straight, or obliquely so [OpL 143–172 (152)]. Proximal cryptocystal shelf as long as or shorter than inner opesial length, flat, gently sloping towards opesia, narrowing on each side towards opesial constriction, surface evenly granular, the granules larger and slab-like where they border the opesia. Operculum flap-like, occupying area of opesia distal to constriction. Articulated pericryptocystal spines 8–14, more or less vertical, mostly all of similar size or the proximal-most spines a little thinner [SpL 178–222]; 1–2 additional spines may be present on gymnocyst, flanking the distalmost pair in ovicelled zooids. No avicularia. Ooecium about as wide as long, smooth-surfaced, with only a thin longitudinal median foramen set within a short elevated crest that extends from the apex of the ooecium to its proximal rim, its opening not closed by zooidal operculum [OoL 243– 278 (255); OoW 244–279 (259)]. Ooecial kenozooid extending outwards around the periphery of the ooecium, a little more so distally, with a mid-distal foramen surrounded by a transversely oval granular cryptocyst flanked by a pair of pore-chamber openings; a pair of spines distal to the kenozooidal foramen. Ancestrula elongate-oval, like later zooids but lacking a cauda, with eight pericryptocystal spines [AnL 332; AnW 212].

Remarks. Because the autozooids have a very short cauda or none at all, they are closer to one another and the colony appears denser than is usual for species of Pyriporoides. Another distinctive feature is the pair of stout articulated spines borne by the ooecial kenozooid.

Distribution. Endemic to West Antarctica, where it is known only from the sea area off Cape Adare, NW Ross Sea, at depths of 151– 623 m.