Powellitheca, 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 : 4-5

Powellitheca gen. nov.

urn:lsid:zoobank.org:act:43B95C9D-F5C5-4802-B508-A952DA9020A6

Type species

Powellitheca terranovae gen. et sp. nov.

Diagnosis

Colony encrusting, with zooids arranged in well-defined longitudinal rows. Zooids with convex, lepralioid frontal shield, regularly and evenly perforated. Lateral zooidal communication through small number of multiporous septula in vertical walls. Orifice dimorphic, wider in maternal zooids. Primary orifice with convex proximal rim and small condyles; not cormidial. Suboral umbo and lyrula present or absent; oral spines lacking. Ovicells hyperstomial. Ooecia of the microporelliform type, large, globular, occupying most of the frontal shield of the next distal zooid. Ectooecium uncalcified. Endooecium thick, granular with deep oval and round pits. Avicularia present or absent, uncommon when present.

Etymology

Named after Neil A. Powell who first described Recent specimens now attributed to this genus in the ‘Terra Nova’ Collection from the Three Kings Islands area, northern tip of New Zealand.

Remarks

The new genus Powellitheca gen. nov. is introduced for three species of cheilostomes from New Zealand, one of which was previously placed in the Australian genus Emballotheca . After comparing these species with a specimen of the type species of Emballotheca , E. quadrata ( Fig. 1 ), it is clear that they differ in several respects, particularly with regard to the morphology of the orifice, ooecium and avicularia. Although both Emballotheca and Powellitheca gen. nov. have enlarged orifices in maternal zooids and a similar orificial shape with a convex proximal lip, Powellitheca gen. nov. lacks the cormidial orifice seen in Emballotheca , as well as the long and robust condyles with very characteristic downwardly directed, scaled tips ( Fig. 1 B–C). Ovicells in Emballotheca are hyperstomial and cleithral. The ooecium is of the lepralielliform type, large, formed by the next distal zooid and occupying its entire frontal shield. The globular ectooecium is calcified, thick-walled, with numerous oval and round pseudopores, in most cases covered by the secondary calcification formed by the four or five distal and distolateral neighboring zooids and separated by thin raised sutures ( Fig. 1 A, D). Secondary calcification corresponds structurally to the zooidal frontal shield and bears pseudopores that are coincident in position with those of the ectooecium. The endooecium is thin and uncalcified (A. Ostrovsky, pers. comm. 2016). Although Powellitheca gen. nov. also has hyperstomial ovicells and the ooecium is similarly large and granular, the ooecia are totally different as they have an uncalcified ectooecium and a calcified endooecium typical of the microporelliform type.

Avicularia in the type species of Emballotheca have a complete crossbar and are directed proximally and towards the midline of the autozooid ( Fig. 1 B, D–E), whereas in Powellitheca gen. nov., when present, they have an incomplete crossbar with short condyles and are distally and outwardly directed. In E. quadrata , avicularia occur constantly paired in female zooids ( Fig. 1 A, D), but in Powellitheca gen. nov. they are uncommon and less regularly placed. Another difference concerns the arrangement of zooidal communication pores in the lateral walls, with numerous, small, oval pore chamber windows in Emballotheca ( Fig. 1 E), but only a few large and consequently more distantly spaced multiporous septula in Powellitheca gen. nov.

Figures

Fig. 1. Emballotheca quadrata (MacGillivray, 1880), NHMUK 1897.5. 1.830, Recent, Port Phillip Heads, Victoria, Australia. A. General view of the colony. B. Autozooidal orifice and avicularia. C. Close-up of a condyle with scaled tip. D. Fertile zooid and surrounding autozooids. E. Large, spatulate, frontal avicularium and lateral pore-chamber windows in the vertical walls. Scale bars: A = 500 µm; B = 40 µm; C = 10 µm; D = 200 µm; E = 100 µm.