Family CLEIDOCHASMATIDAE Cheetham & Sandberg, 1964

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Introduction

The family Cleidochasmatidae was established by Cheetham & Sandberg (1964) for Cleidochasma Harmer (1957). The family also included species which have since been referred to the genera Paracleidochasma and Schedocleidochasma by Soule et al. (1991), both of which belong to the Phidoloporidae. In fact, only Cleidochasma sensu stricto, with its two species, C. protrusum (Thornely) and C. suluense Soule et al., can at present be unequivocally assigned to the Cleidochasmatidae. Gordon (1993) who considered cleidochasmatid morphology in relation to the phidoloporids, took a narrower view than Soule et al., but two of the genera he included, Anchicleidochasma and Cleidochasmidra, require examination of type material before their position can be ascertained. The third genus included by Gordon, Hippoporella, he assigned to the Phidoloporidae in 1984, and does not seem to have much in common with C. protrusum, the type species of Cleidochasma.

Two fossil species from Victoria, Characodoma excubans (Waters) and C. rotundum (MacGillivray) do, however, have a close relationship with Cleidochasma protrusum, which appears to be congeneric with them. Cook & Bock (1996) have redescribed all three species and treated Cleidochasma as a junior objective synonym of Characodoma. The name of the family remains unchanged (ICZN 1999, art. 40.1). Gordon & d'Hondt (1997) described four species of Characodoma from the Philippines.

The cleidochasmatids, as defined here, are encrusting, with unilaminar to multilaminar sheets of zooids. The frontal shield is cryptocystidean, with marginal septular pores defined by areolae. The shield typically develops a secondary aragonitic outer layer, which in Characodoma excubans is tuberculate and almost spinous. The primary orifice has a distinct sinus, defined by prominent condyles, and often appears to be keyhole-shaped (cleithridiate). Distally the orifice is smooth, not beaded. The ovicell is hyperstomial, very prominent, tuberculate and minutely punctate; and may be thinly calcified proximally.

The Australian fauna is still uncertain; encrusting forms from both Bass Strait and south Western Australia appear to belong to the family, but are undescribed.

Diagnosis

Colony moderately well calcified, encrusting, with small erect expansions. Zooids with a lepralioid frontal shield, with marginal areolae, becoming secondarily thickened by a tuberculate outer layer. The primary orifice has a distinct sinus with paired condyles. Avicularia are often paired and oral, or frontal. The ovicells are hyperstomial, prominent and globular, with a porous frontal.

General References

Cheetham, A.H., & Sandberg, P.A. 1964. Quaternary Bryozoa from Louisiana mudlumps. Journal of Paleontology 38: 1013-1046

Cook, P.L., & Bock, P.E. 1996. Characodoma Maplestone, a senior synonym of Cleidochasma Harmer (Cleidochasmatidae). pp. 81-88 in Gordon, D.P., Smith, A.M., & Grant-Mackie, J.A. (eds). Bryozoans in Space and Time. Wellington : NIWA.

Gordon, D.P. 1984. The marine fauna of New Zealand: Bryozoa: Gymnolaemata from the Kermadec Ridge. New Zealand Oceanographic Institute Memoir 91: 1-198

Gordon, D.P. 1993. Bryozoan frontal shields: studies on umbonulomorphs and impacts on classification. Zoologica Scripta 22: 203-221

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

Soule, John D., Soule, Dorothy F., & Chaney, Henry W. 1991. New tropical Pacific and Indian Ocean Cleidochasmatidae (Cheilostomata: Ascophora). pp. 465-486 in Bigey, F.P., & d'Hondt, J.-L. (eds). Bryozoaires Actuels et Fossiles: Bryozoa Living and Fossil. Bulletin de la Societe des Sciences Naturelles de l'Ouest de la France Mémoire HS 1. Nantes : Société des Sciences Naturelles de l'Ouest de la France.

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