Family CHLIDONIIDAE Busk, 1884

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Family CHLIDONIIDAE Busk, 1884

Compiler and date details

July 2001 - Dr Philip Bock

Introduction

The family Chlidoniidae was introduced by Busk (1884) for the genus Chlidonia, first named informally by Lamouroux (1824). His use, and that of d'Orbigny (1851), predates the name Cothurnicella, which was introduced by Wyville Thomson in 1858, for a species he called C. daedala, from Western Australia (MacGillivray 1885). Chlidonia is regarded as monospecific, C. pyriformis having a world-wide, warm-water distribution (Harmer 1926; Gordon 1989). The morphology of C. pyriformis (as C. cordieri) has been described in detail by Levinsen (1909). In 1926, Harmer added the genus Crepis Jullien (1883) to the family.

The Chlidoniidae is characterised by small, pear-shaped zooids with a cryptocyst lamina which extends almost to the region beneath the operculum. Colonies are usually erect, branched and nodal, the zooids uniserial or biserial, but they may be repent, the zooids having long tubular extensions proximally. Apart from the cryptocyst, all calcified walls are exterior gymnocyst.

Chlidonia pyriformis has only 8 tentacles, and a very small tentacle crown (Winston 1978). Vicarious avicularia are sometimes present in species of Crepis, but are absent in Chlidonia. Brooding zooids, where known, are longer and markedly deeper than autozooids, and the embryo develops in an interior ovisac (Harmer, 1926; Gordon, 1989).

Chlidonia pyriformis has an extensive distribution, and was found by Gordon (1989) to be part of a cryptofauna on reef flat rubble. It occurs from Western Australia, Torres Strait, and Victoria (MacGillivray, 1885). Repent colonies of Crepis longipes and C. verticillata were listed by Harmer (1926) from Darwin and Torres Strait respectively. The earliest record of Crepis is Miocene and that of Chlidonia (as Cothurnicella ) is Upper Eocene (Lagaaij 1968).

Diagnosis

Colony erect or adnate, jointed. Internodes single or double zooecia, with tubular proximal part expanding distally, with elliptical area covered by frontal membrane. Cryptocyst extensive, with small semicircular to oval opesia, and in one species with small pores, possibly opesiules. Vicarious avicularia known in one species. Brooding internal, in enlarged zooids. Kenozooids in some branch segments, and in jointed filiform branch terminations.