Family DITAXIPORIDAE Stach, 1935

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Family DITAXIPORIDAE Stach, 1935

Compiler and date details

July 2001 - Dr Philip Bock

Ditaxiporinae Stach, L.W. 1935. The genera of Catenicellidae. Proceedings of the Royal Society of Victoria 47(2): 389-396 [394].
Ditaxiporinidae Cheetham, A.H. 1963. The polyzoan genus Ditaxiporina Stach. Annals and Magazine of Natural History 13 5: 485-490 [489].

Introduction

The family Ditaxiporidae was defined by Stach (1935) for the genera Ditaxipora MacGillivray 1895 and Ditaxiporina Stach, 1935. Subsequently, the family Ditaxiporinidae was introduced by Cheetham (1963) for the fossil genera Ditaxiporina Stach and Caberoides Canu. Gordon & Braga (1994) included the fossil genera Ditaxipora MacGillivray, Plagiopora MacGillivray and a new genus, Ahcheethamia, together with a new Recent genus, Bryosartor, in the Ditaxiporinae, defined as a subfamily of the family Catenicellidae. Although there is some overlap in characters between these two groups, there are several sets of consistent differences, and the Ditaxiporidae is regarded here as a separate family, including the subfamily Vasignyellinae, which Gordon & Braga (1994) defined as a subfamily of the Catenicellidae.

Ditaxipora and Plagiopora are known from the Australian Tertiary, and Plagiopora recens occurs from deep water north of Norfolk Island (Gordon 1989). The Recent species Bryosartor sutilis was described from deep water off New Caledonia by Gordon & Braga (1994), and both the living forms may well be found in the lower slope depths off northeastern Australia in the future.

Colonies are nodal, with multizooidal, biserial internodes. Bryosartor sutilis has a costate frontal shield and shallow frontal pore chambers, one of which gives rise to an avicularium. Ovicells are enormous, with a large entooecial frontal area. Basally the zooid walls are all exterior. Plagiopora recens differs in having no costal elements of frontal shield, but large, shallow pore chambers which also cover the basal walls. Ovicells have not been found.

Vasignyella is almost certainly related to the fossil genus Ditaxiporina, although 'not derived directly but from a common predecessor' (Gordon & Braga 1994). Vasignyella has been assigned to the Savignyellidae, but differs in important respects and has several characters linking it with both the Catenicellidae and Ditaxiporidae.

Vasignyella otophora has uniserial, nodal colonies, which are anchored by delicate cuticular rhizoids and are inconspicuous. The zooids are vase-shaped, with an elongated tubular portion proximally, and a gymnocyst with large pores scattered over the surface. The proximal side of the orifice is formed by the fusion of a pair of vestigial costae. There are a pair of lateral oral avicularia, which are associated with a single pair of frontal pore chambers. Five pairs of uniporous chambers are arranged in a lateral series. Ovicells are unknown.

V. otophora has a wide Indo-west Pacific distribution in shallow, reef conditions, and was reported for the first time from Australia by Ryland & Hayward (1992) from the Great Barrier Reef.

Diagnosis

Colony erect, attached by basal rhizoids, jointed, internodes thinly calcified, alternating with cuticular nodes. Zooids biserial, facing one way, with an extensive frontal shield formed by a gymnocyst or fused costal spines. Opesia small. Dorsal surface sometimes covered by a large pore-chamber. Avicularia frontal and basal, adventitious. Ovicell, when present, hyperstomial, with an endooecial frontal area. (after Gordon & Braga, 1994).