Steginoporella modesta Gordon & Voje & Taylor 2017, n. sp.

Steginoporella modesta n. sp.

(Figs 1E, 21, 23)

Etymology. Latin modestus, modest, unassuming, alluding to the small size of the colony.

Material examined. Holotype: NIWA23304, TAN0413 /109, 37.549° S, 176.988° E, west of White Island, Bay of Plenty, 13 November 2004, 142 m. Paratype: NIWA 122576, same data as for holotype.

Description. Colony encrusting, comprising small lobate to sublinear pluriserial growths not more than six zooids across, up to 19 mm long and 5 mm wide. Colour of dried colonies pale brownish-beige.

Zooids monomorphic, roundly hexagonal, with one of the pair of daughter zooids at the bifurcation of a zooid row more or less parallel-sided, with mostly arcuate distal and proximal margins (mean L/W = 1.45); widest mostly about mid-length. Cryptocystal area more than half zooid length, extensive shelf sunken, weakly concave, mostly granular-tubercular, with sloping pseudoporous semicircular area proximal to median process.

Opercular area delimited proximally by stout triangular pivots; median process with distolateral ‘wings’ that do not reach pivots or lateral margins; proximomedial foramen of small to moderate size. Inner face of operculum smooth, lacking sclerites.

Polypide not seen. Ancestrula smaller than other zooids but resembling them, deep-bodied, the sides interiorwalled and granular; smooth thin margins of frontal cryptocyst on both sides converging without meeting proximally, descending to substratum, with narrow granular strip between. First daughter zooid budded laterally, followed near-simultaneously by distolateral pair from ancestrula.

Measurements. In micrometres: ZL 1092±173, 932–1389 (4, 10); ZW 751±86, 643–912 (4, 10); OpL 310±43, 256–367 (1, 10);OpW 513±33, 456–557 (1, 10). AnL 978, AnW 400.

Remarks. Colonies of S. modesta n. sp., like those of Steginoporella lineata n. sp., another deep-sea species (see below), are very small and somewhat narrow. Unlike S. lineata n. sp., zooids of S. modesta n. sp. are monomorphic. The species is evidently pigmented in life—while a specimen was being prepared for SEM the bleaching solution turned pale purple. All specimens, including a small ancestrulate colony, were loose in the sample but their undersides are carpeted by a thin layer of sponge spicules, indicating the apparent substratum in life.

Distribution. Endemic to New Zealand, being known only from the type locality in the Bay of Plenty; 142 m.