Family LUNULARIIDAE Levinsen, 1909

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Family LUNULARIIDAE Levinsen, 1909

Compiler and date details

July 2001 - Dr Philip Bock

Lunulariidae Levinsen, G.M.R. 1909. Morphological and systematic studies on the cheilostomatous Bryozoa. Copenhagen : Nationale Forfatteres Forlag 431 pp. [155].

Introduction

The family Lunulariidae was introduced by Levinsen (1909), somewhat informally, for the genera Cupularia (=Cupuladria) and Lunularia, with the words 'It will perhaps be justifiable to combine the two genera ... into one family Lunulariidae'. Busk (1884) had introduced Lunularia for L. capulus, which he had earlier (1852 and 1854) referred to Lunulites, and Levinsen mentioned only Lunularia capulus in his discussion. Lunularia was used by Cook & Chimonides (1986) to accommodate three Australasian species, L. capulus, L. repanda (Maplestone 1904) and L. parvicella (Tenison Woods, 1880). Although all three species are known as Tertiary fossils from Australia, only L. capulus and L. repanda also occur in Recent seas. L. repanda is known from the Tertiary and Recent of New Zealand.

Colonies of Lunularia are the largest lunulites found in Australia and may have a diameter of 50 mm. They are budded radially, and the dark, paddle-shaped mandibles of the large, often vicarious avicularia, are obvious to the naked eye. They form contiguous radial series, alternating with the autozooids in L. capulus, but are scattered in L. repanda. Colonies are light brown to dark orange in colour.

Species of Lunularia and Kausiaria are unusual among lunulites in developing from an ancestrula which apparently has no substratum. One species of Cretaceous European Lunulites also has this type of early astogeny (Håkansson 1975), but has much smaller colonies. Colonies of Lunularia also produce basal buds, leading to the development of small, fan-shaped subcolonies, usually starting with an avicularium, from the basal extrazooidal coelom. It is presumed that these break off and have a separate existence, like those produced by Otionellina squamosa and Petasosella moderna. These can originate from a fragment consisting of only one avicularium and autozooid, broken from the periphery of a colony (Cook & Chimonides 1985; Bock & Cook 1998).

Autozooids have a large opesia, and the cryptocyst may be marginally serrated, even dentate proximally. Brooding zooids are very large, almost twice the size of autozooids frontally, and have an even more enlarged cystid cavity, which impinges on those of neighbouring autozooids and avicularia. Distally, the brooding zooids are raised to form a minute 'vestigial' ovicell which is closed by the operculum. Brooding zooids may occur in concentric series, but are generally scattered, and do not form distinct astogenetic zones as in Selenaria and Otionellina. The embryos are enormous and nearly fill the brooding zooid cystid; they are deeply pigmented, and are presumably contained within an interior ovisac.

Although the larval life and settlement have never been described, Håkansson (1981) observed that minute, ancestrulate colonies have been discovered among the sand grains adhering to the basal side of some dried colonies of L. capulus. In view of the lack of sand grain substratum in colonies, it is possible that some form of protection for the metamorphosing larvae is provided beneath the 'parent' colony, but the entire subject needs observation of living specimens.

Avicularian mandibles are paddle-shaped, and, compared with those of Petasosella and Selenaria, are relatively short. They are hooked or trifurcate terminally and are slung on very slight symmetrical condyles. The opesiae are large and simple.

Of the two Recent species, L. capulus seems to have the widest range, occurring from Queensland, and from Western Australia across the southern coasts to New South Wales. Like L. repanda, it is very common off South Australia and Victoria. Bock (1982) gave a maximum depth of 35 m , but some specimens from 167 m have been collected, apparently alive, from off Western Australia.

The fossil species L. parvicella, occurs widely from the Victorian and South Australian Tertiary deposits. It has even larger avicularia than L. repanda and the autozooids have a distinct proximal cryptocyst.

Diagnosis

Colony free-living, high-domed, hollow basally, budded radially from ancestrula with no solid substratum. Autozooids with large opesia, sometimes with a proximal expansion of cryptocyst. Avicularia large, in separate radial rows or included in rows of autozooids; mandible long and thickened. Brooding zooids large, interspersed with autozooids, with small cavity at distal end. Embryos very large, filling entire brooding zooid cavity. Colony regeneration from basal buds, and possible from small fragments.