Steginoporella modesta, Gordon & Voje & Taylor, 2017

Gordon, Dennis P., Voje, Kjetil L. & Taylor, Paul D., 2017, Living and fossil Steginoporellidae (Bryozoa: Cheilostomata) from New Zealand, Zootaxa 4350 (2), pp. 345-362 : 355-356

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.

Figures

FIGURE 1. Six species of Recent New Zealand Steginoporella (NIWA stations in parentheses). A, S. neozelanica (TAN 1105 / 27); B, S. marcusi (respectively from three localities, left to right, D 896, TAN 1105 / 42, TAN 1105 / 60); C, S. perplexa (small colony from Z 15617); D, S. discors n. sp. (TAN 0906); E, S. modesta n. sp. (TAN 0413 / 109); F, S. lineata n. sp. (TAN 0205 / 64). All to same scale (scalebar 25 mm).

FIGURES 20 – 25. Zooids of New Zealand Steginoporella (NIWA stations in parentheses). 20, S. discors n. sp. (Z 9743); 21, 23, S. modesta n. sp., respectively showing autozooids and an ancestrula and daughter zooid (TAN 0413 / 109); 22, 24 – 25, S. lineata n. sp., showing autozooids and larger avicularian B-zooids (TAN 0205 / 64). Figs 20 – 22 at same scale (scalebar 1 mm); scalebars 0.5 mm in figs 23 – 25.