Family ASCOSIIDAE Jullien, 1883

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Family ASCOSIIDAE Jullien, 1883

Compiler and date details

July 2001 - Dr Philip Bock

Introduction

The family Ascosiidae was introduced in a list of classifications by Jullien (1883) but was not mentioned in his description of the genus Ascosia and its type species A. pandora. Ascosia pandora is a delicately calcified, lunulitiform, deep-water species from the north-eastern Atlantic; its colonies are anchored by basal rhizoids. The autozooids are semi-erect and discrete, in contact only at the basal part of the vertical walls, where they communicate through large, chambered pores. The ovicells are large and globular, hyperstomial and closed by the operculum; there is a lateral oral adventitious avicularium with an acute mandible orientated distally (Harmelin 1977). In spite of these distinctive characters, A. pandora shares a suite of strong similarities with the lunulitiform genus Anoteropora, which differs in having robust, well-calcified colonies. Cook & Chimonides (1994) noted these similarities, together with those of the Eocene genera Kionidella and Stenosipora, but were unaware of Jullien's family name. They placed all three genera in the family Mamilloporidae. Mamillopora, although sharing many of the characters of Anoteropora and the other genera, differs completely in the nature and position of its avicularia. It seems more appropriate to assign Anoteropora to the Ascosiidae, in spite of Harmer's (1957) disclaimer of any relationship between Ascosia and Anoteropora .

The genus Anoteropora has an extensive fossil and Recent range. One species, A. magnicapitata, occurs in the Indian Ocean and southwest Pacific and was recorded from Torres Strait by Kirkpatrick (1890), as Stichopora simplex. Colonies are well calcified, with a maximum diameter of about 25 mm. They are domed frontally and budded radially. The vertical walls are deep, and the large autozooid orifices open almost in the centre of the restricted frontal shield of the semi-erect zooids. The concave surface is formed by a mosaic of exterior basal walls. Zooids communicate through a ring of large chambered septular pores placed at the base of the vertical walls. Septular pores in the basal walls give rise to rhizoids which anchor the colony in the sediment. The avicularia are adventitious, usually lateral and oral, and orientated distally; they have acute, sometimes hooked mandibles, hinged on a bar. Ovicells are large, globular and very prominent early in ontogeny; they are imperforate and are closed by the operculum.

Anoteropora is distributed in the eastern Atlantic and Indo-West Pacific, including South Africa. Closely related fossil genera occur in Europe and the Mediterranean, in Eocene to Pliocene deposits (Cook & Chimonides 1994).

Diagnosis

Colony lunulitiform, concave, free-living, usually well calcified, occasionally delicate, anchored by basal rhizoids. Zooids budded radially, frontal shield lepralioid, pores marginal, orifice large, central, with condyles. Avicularia large, adventitious, oral, rigidly patterned. Brooding zooids enlarged, ovicells very large, hyperstomial, with porous frontal.