Family SIPHONICYTARIDAE Harmer, 1957

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• Siphonicytaridae Harmer, S.F. 1957. The Polyzoa of the Siboga Expedition. Part 4. Cheilostomata Ascophora II. Siboga-Expéditie Report 28D: 641-1147 [892].

Introduction

The family Siphonicytaridae was introduced by Harmer (1957) to accommodate S. serrulata, the type species of Siphonicytara, collected by the 'Challenger' and described by Busk (1884), and two other species collected in the same area by the 'Siboga' The genus has since been revised by Bock & Cook (2001) and includes several Recent and fossil Australian species, and some other fossil genera.

Siphonicytara is characterised by erect, branched colonies; some delicate and quadriserial, others robust and multizooidal, which may be anchored by rhizoids. The branches are cylindrical or slightly flattened, with the zooids on either face sometimes differing morphologically from each other. The frontal shields of autozooids have large marginal septular pores, an ascopore, and long, but not prominent peristomes. Nearly all the calcified walls are interior, even the peristomes being surrounded by an extension of the frontal hypostegal coelom.

The ascopore and frontal septular pores are surrounded by raised calcified walls (septa) which project from the calcified frontal shield into the hypostegal coelom forming compartments beneath the loosely investing cuticle. The ascopore originates just proximally to the primary orifice but increasing length of peristome and depth of frontal calcification results in its appearing to open in the proximal part of the exposed frontal shield. Small avicularia arise from marginal septular pores; the mandibles slung on a bar. The method of brooding is unknown, but may be in interior ovisacs or diverticula of the concealed distal peristome wall. Continued ontogenetic thickening of the calcification often results in all recognisable features of zooids becoming obscured.

Siphonicytara is known from abyssal depths from the East Indies and western Indian Ocean. Six species have recently been described from New Caledonia and New Zealand by Gordon & d'Hondt (1997). One species occurs from Western Australia at shelf depths, from 119-137 metres. Its colonies, like those of some of the deep-water species, are anchored by rhizoids. Fossil species are known from the Eocene of Tonga, and are widely distributed in Victoria and South Australia in Upper Eocene to Miocene deposits. They include records once attributed to the unrecognisable genus Tubitrabecularia (Bock & Cook 2001).

The relationships of the Siphonicytaridae are obscure, but two other fossil genera, with closely similar characters, Gastroporella and Tubucella, may be assigned to the family, increasing its geographical and stratigraphic range to the Eocene of Europe and North America.

Diagnosis

Colony erect, branched, arising from an erect ancestrula, well calcified, sometimes massive, often anchored by rhizoids. Zooids with lepralioid frontal shields, marginal areolae and an ascopore, orifice with a peristome. Secondary calcification producing raised, anastomosing septal ridges over the branch surface. Avicularia usually small, adventitious, oral or sutural. Ovicells unknown, inferred to be peristomial.

General References

Bock, Philip E., & Cook, Patricia L. 2001. A review of Australian Siphonicytara Busk (Bryozoa: Cheilostomatida). Records of the Western Australian Museum 20: 307-322

Busk, G. 1884. Polyzoa. Pt. I. Cheilostomata. Report on the Scientific Results of the Voyage of H.M.S. Challenger 1873–1876, Zoology 10: xiv, 216

Gordon, D.P., & d'Hondt, J.-L. 1997. Bryozoa: Lepraliomorpha and other Ascophorina from New Caledonian waters. (Résultats des Campagnes MUSORSTOM, Vol. 18, Crosnier, A., ). Mémoires du Muséum national d'Histoire naturelle, Paris [1936-1950] 176: 9-124

Harmer, S.F. 1957. The Polyzoa of the Siboga Expedition. Part 4. Cheilostomata Ascophora II. Siboga-Expéditie Report 28D: 641-1147

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