Powellitheca terranovae, Emanuela Di Martino, Paul D. Taylor, Dennis P. Gordon & Lee Hsiang Liow, 2016

Emanuela Di Martino, Paul D. Taylor, Dennis P. Gordon & Lee Hsiang Liow, 2016, On Powellithecidae fam. nov., a new Pliocene to Recent bryozoan family endemic to New Zealand, with the description of Powellitheca gen. nov. (Bryozoa, Cheilostomata), European Journal of Taxonomy 207, pp. 1-17 : 5-8

Powellitheca terranovae gen. et sp. nov.

urn:lsid:zoobank.org:act:F8CC3594-F2CB-4E98-945E-800B0C2A460C

Figs 2 A–F, 7, Table 1

Emballotheca waipukurensis – Powell 1967: 336, fig. 87. — Gordon 1989: 36, pl. 17, figs E–F. — Gordon et al. 2009: 291.

Diagnosis

Colony encrusting. Zooids rectangular, arranged in well-defined rows. Frontal shield convex, regularly and evenly perforated, apart from a narrow peristomial area lacking pores, granular. Small, frontal, multiporous septula at the distolateral and proximolateral corners of the zooids. Lateral zooidal communications through multiporous septula visible on the vertical walls. Orifice with a convex proximal lip and two small, lateroproximally placed condyles, bearing an anvil-shaped median lyrula directed downwards and not visible in frontal view. Oral spines absent. Ooecium large, globular, occupying most of the frontal shield of the next distal zooid, porous and granular with the same texture as the frontal shield. Avicularia uncommon, single or paired, with short condyles and tapered rounded rostrum distolaterally directed.

Etymology

Named after the ‘Terra Nova’ Expedition, the source of several specimens of this species described initially by Powell (1967).

Material examined

Holotype

NEW ZEALAND: NIWA 98983, Recent, 2 Dec. 1981, Stephens Hole, Cook Strait, NZOI Station Q686, 40˚41.3' S, 174˚03.8' E, 205 m.

Description

Colony encrusting, multiserial, unilaminar; colour yellow. Ancestrula not observed. Zooids arranged in well-defined rows ( Fig. 2 A), distinct, boundaries marked by very narrow furrows, quadrate to rectangular generally with squared corners, straight or curved zooidal lateral boundaries, longer than broad (mean L/W = 2.02). Polypides with 19 tentacles. Frontal shield lepralioid, convex, granular, regularly and evenly perforated by 50–80 small, circular or slit-like pseudopores about 15–20 μm in diameter ( Fig. 2 B). Small, rounded triangular, multiporous frontal septula, bearing three or four inconspicuous pores, about 5–6 μm in diameter, placed at distolateral and proximolateral zooidal corners ( Fig. 2 B), often hidden in ovicellate zooids owing to a different surface topography in that area. Orifice placed distally, generally broader than long, with the proximal rim gently convex and two tiny condyles placed proximal to the mid-lateral position; an imperforate, granular, slightly raised peristomial rim surrounding the orifice ( Fig. 2 E). An anvil-shaped lyrula, placed medially, 60–90 μm broad, occupies about half of orifice width, directed downwards, vertically or distovertically, and not visible in frontal view ( Fig. 2 E). Oral spines and suboral umbo absent. Ovicells hyperstomial. Ooecia globular, large, occupying almost the entire frontal shield length of the next distal zooid forming the ooecium. Ectooecium uncalcified. Endooecium thick, granular like the frontal shield but with a finer granulation, with deep oval and round pits (11–20 μm in diameter) and with a proximal, granular, imperforate band and a narrow, smooth, frontal rim, slightly upturned ( Fig. 2 A, C, F). Primary orifice of fertile zooids larger than that of autozooids, rounded quadrangular, slightly broader than long with a smooth, stout suboral umbo ( Fig. 2 A, C, F); secondary orifice slit-like ( Fig. 2 A). Avicularia uncommon, adventitious, usually single, rarely paired, lateral to the orifice, on or adjacent to ovicellate zooids, distolaterally directed, with short condyles, no calcified crossbar, rounded tapered rostrum ( Fig. 2 D). Oval, multiporous (at least 14 pores) septula in lateral vertical walls, about 95–120 μm long by 45–55 μm wide ( Fig. 2 C). Intramural, reparative budding observed ( Fig. 2 A).

Remarks

Originally included in the ‘ Emballotheca waipukurensis group’ together with the Plio–Pleistocene P. waipukurensis comb. nov. (see description below), the Recent specimens now assigned to P. terranovae gen. et sp. nov. differ from true P. waipukurensis comb. nov. in having an anvil-shaped median lyrula that is difficult to observe in frontal view because it is directed either vertically downwards or only slightly distally angled. Further differences are the lack of a suboral umbo in the non-ovicellate zooids of P. terranovae gen. et sp. nov., a feature that in this species is restricted to the female zooids, and the different shape of the avicularium rostrum, which is spatulate in P. waipukurensis comb. nov. but distally tapered and rounded in P. terranovae gen. et sp. nov. They also differ in the size of the zooids, orifice and ooecia, which are slightly larger in P. terranovae gen. et sp. nov.

Distribution

This species is known from the Cook Strait area and the Three King Islands, from 75 to 205 m depth.

Figures

Fig. 2. Powellitheca terranovae gen. et sp. nov. NIWA 98983, Recent, Stephens Hole, NZOI Station Q 686, New Zealand. A. Group of fertile zooids and autozooids. B. Close-up of an autozooid showing frontal, multiporous septula on the distolateral corners. C. Lateral, multiporous septula on the vertical walls of a maternal zooid. Note also the prominent, suboral umbo. D. Avicularium. E. Tilted view of an autozooidal orifice to show the anvil-shaped, downwardly directed lyrula. F. Orifice of a maternal zooid and incomplete ooecium. Scale bars: A = 250 µm; B – C = 100 µm; D – E = 50 µm; F = 150 µm.

Tables

Table 1. Measurements in microns of Powellitheca terranovae gen. et sp. nov.

	N (zooids, colonies)	Mean	SD	Min	Max
ZL	20, 1	636	± 80	522	824
ZW	20, 1	315	± 49	233	410
OL	20, 1	126	± 12	111	156
OW	20, 1	167	± 8	158	189
OL*	13, 1	223	± 18	200	267
OW*	10, 1	242	± 24	179	264
OvL	9, 1	489	± 31	444	544
OvW	16, 1	432	± 25	400	468
AvL	4, 1	186	± 10	177	198
AvW	4, 1	94	± 12	59	91