Tuesday, June 28, 2016

[Invertebrate • 2016] On Powellithecidae fam. nov., A New Pliocene to Recent Bryozoan Family (Bryozoa, Cheilostomata) Endemic to New Zealand, with the Description of Powellitheca gen. nov.

Powellitheca terranovae  
Martino, Taylor, Gordon & Liow, 2016


A new cheilostome bryozoan genus, Powellitheca gen. nov., is erected here for three species from New Zealand, one of which has been previously assigned to Emballotheca Levinsen, 1909, but which differ significantly from the Australian type species of EmballothecaEquadrata (MacGillivray, 1880). Notably, whereas Emballotheca has a cormidial orifice (i.e., formed by numerous neighbouring zooids), and lepralielliform ooecia, the orifice of Powellitheca gen. nov. is formed by single zooids and ooecia are of the microporelliform type. The introduction of a new family, Powellithecidae fam. nov., becomes necessary because of the nonconformity of Powellitheca gen. nov. with other known families having microporelliform ooecia. In addition to the Recent type species Powellitheca terranovae gen. et sp. nov., one other new Recent species, P. labiosa gen. et sp. nov., and a Plio-Pleistocene fossil species, Monoporella waipukurensis Waters, 1887, are assigned to the new genus.

Keywords: Cheilostomata, Powellithecidae, Plio-Pleistocene, Recent, Wanganui Basin.

Order Cheilostomata Busk, 1852
Superfamily Smittinoidea Levinsen, 1909

Family Powellithecidae fam. nov.

Type genus: Powellitheca gen. nov.

Diagnosis: See genus diagnosis below.

Remarks: Powellithecidae fam. nov. is erected to accommodate the new genus Powellitheca gen. nov., characterised by a unique suite of morphological characters when compared with all the known families sharing the same microporelliform ooecial structure. The microporelliform ooecium consists of an uncalcified ectooecium and a calcified endooecium separated by a narrow coelomic space in communication with the hypostegal coelom of the distal autozooid, and has been found only in the lepraliomorph families Microporellidae Hincks, 1879, Pacificincolidae Liu & Liu, 1999, Schizoporellidae Jullien, 1883, Myriaporidae Gray, 1824 and Porinidae d’Orbigny, 1852 (Ostrovsky 2013). Powellitheca gen. nov. cannot be accommodated in any of these families. It lacks the ascopore typical of Microporellidae and the small heterozooid (avicularium or kenozooid) placed between the orifice and the umbo seen in Pacificincolidae. In Schizoporellidae the orifice has well-defined condyles separating a distinct anter from a small sinus, while the orifice in Powellitheca gen. nov. is dimorphic, condyles are faint and a sinus is lacking. An orifice with sinus and condyles also characterises Myriaporidae from which Powellitheca gen. nov. further differs in having multiporous instead of uniporous septula. Porinidae typically have erect colonies, a primary orifice with a well-defined sinus, a well-developed aviculiferous peristome, and a short frontal spiramen. 

Powellitheca gen. nov.

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. 

Fig. 7. Powellitheca terranovae gen. et sp. nov. Underwater photograph taken by Dr. Vincent Zintzen (Department of Conservation, NZ) at the Poor Knights Islands, off the NE coast of North Island, north of Auckland, New Zealand. Note the band of yellow pigment at the colony’s growing edges and the 19 yellow tentacles of the autozooids.

Powellitheca terranovae gen. et sp. nov.

Figs 2A–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).

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

Powellitheca labiosa gen. et sp. nov.
Fig. 3A–F, Table 2
Diagnosis: Colony encrusting. Zooids polygonal, arranged in well-defined rows. Frontal shield markedly convex, regularly and evenly perforated, smooth. Small, frontal, multiporous septula at the distolateral and proximolateral zooidal corner. Lateral zooidal communications through small multiporous septula visible on the vertical walls. Orifice with a weakly convex proximal lip and two small latero-proximally placed condyles; lyrula and oral spines absent. Primary orifice hidden by a flat, imperforate, finely granular, projection of the peristome present in both ovicelled zooids and autozooids. Ooecium large, globular, occupying most of the frontal shield of the next distal zooid, porous and granular. Avicularia absent.

Etymology: The name of the species derives from the Latin adjective labiosus, -a, -um meaning ‘with a large lip’, and refers to the flat, labrum-like projection of the peristome covering the primary orifice. 

Distribution: This species is known only from the South Maria ridge, NE of the Three King Islands.

Powellitheca waipukurensis (Waters, 1887) comb. nov.
Figs 4, 5A–D, 6, Table 3
Monoporella waipukurensis Waters, 1887: 50, pl. 6, fig. 11.
Hippoporina? waipukurensis – Brown 1952: 272, figs 203–204.
Emballotheca waipukurensis – Gordon et al. 2009: 296. — Rust & Gordon 2011: 156.

Distribution: This species has been found in the Mangapanian Te Aute Limestone (Pliocene, ~ 3.1 Ma) of Waipukurau Gorge and nearby Hatuma Quarry, Hawkes Bay, and in the Nukumaruan (early Pleistocene) Nukumaru Limestone (~ 2.3–2.0 Ma) and Nukumaru Brown Sand (~ 2.0–1.9 Ma) units of Nukumaru and Waiinu beaches, Wanganui Basin, and Nukumaruan at Petane (trigonometrical station), just north of Napier, Hawkes Bay, New Zealand.

Martino, Emanuela D., Paul D. Taylor, Dennis P. Gordon and Lee H. 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): 1-17. DOI: 10.5852/ejt.2016.207