Family CREPIDACANTHIDAE Levinsen, 1909

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Introduction

Levinsen (1909) introduced the family Crepidacanthidae for his genus Crepidacantha alone. Bassler (1953) included several additional genera, but when Brown reviewed the genus in 1954, he rejected these, considering the family as monogeneric. The earliest Australian record attributable to Crepidacantha was of a species described as Lepralia setigera by MacGillivray from Port Phillip in 1883.

Crepidacantha is characterised by encrusting colonies, the zooid frontal shield being imperforate except for marginal frontal septulae, which extend distally round the orifice, which has well-developed lateral condyles. Zooids communicate through pore-chambers, which form a circlet round the basal wall. Avicularia are latero-oral, and paired, each derived from a frontal septula. Mandibles are often elongated and setiform. The ovicell is developed from a distally enlarged maternal zooid, and its ontogeny is complete before the next zooid is budded distally ('recumbent'); there is an entozooidal porous frontal area. One of the most distinctive features of the genus can usually only be seen early in ontogeny of the zooids. Each zooid develops a circle of marginal cuticular spinous processes from the lateral walls, between the pore-chambers and the frontal septulae. These may become partially calcified, but are usually lost later in ontogeny. It is possible that they assist the growing edge of the colony to combat competition from other species.

The genus Crepidacantha has a world-wide distribution in tropical and subtropical shelf waters, particularly on coral (Winston 1986). Species are present in the Miocene and Pleistocene deposits of New Zealand (Brown 1954). More than a dozen species have been described and at least four of these occur in Australia. The majority of records are from Victoria, New South Wales, and Queensland (Ryland & Hayward 1992). Two Victorian species are known only from Australia, these being C. bracebridgei and C. kirkpatricki (Brown, 1954).

Diagnosis

Colony well calcified, encrusting, often associated with corals. Zooids with a lepralioid frontal shield, with marginal pores only, intercommunicating through prominent pore chambers. Cuticular spines surrounding each zooid present early in ontogeny. Avicularia paired, oral, usually with setiform or elongated mandibles. Ovicells 'recumbent' with a porous frontal area of entooecium.

General References

Bassler, R.S. 1953. Bryozoa. Treatise on Invertebrate Paleontology, Part G, Moore, R.C., (editor). Lawrence, Kansas : Geological Society of America pp. G1-G253.

Brown, D.A. 1954. On the polyzoan genus Crepidacantha Levinsen. Bulletin of the British Museum (Natural History) Zoology 2(7): 243-263

Levinsen, G.M.R. 1909. Morphological and systematic studies on the cheilostomatous Bryozoa. Copenhagen : Nationale Forfatteres Forlag 431 pp.

Macgillivray, P.H. 1883. Descriptions of new or little-known Polyzoa. Part 2. Transactions and Proceedings of the Royal Society of Victoria 19: 130-138

Ryland, J.S. & Hayward, P.J. 1992. Bryozoa from Heron Island, Great Barrier Reef. Memoirs of the Queensland Museum 32(1): 223-301

Winston, J.E. 1986. An annotated checklist of coral-associated bryozoans. American Museum Novitates No. 2859: 39 pp.

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