Family ISCHNOCHITONIDAE

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Family ISCHNOCHITONIDAE

Introduction

The Ischnochitonidae is a very large family found worldwide in tropical to polar seas, from the littoral zone to a depth of over 100 m. The family is characterised by insertion plates with slits on all valves, multislits on terminal valves and one or more slits on intermediate valves, insertion plate teeth not pectinate.

The family is divided into six subfamilies, five of which occur in Australian waters.

The Ischnochitoninae is a large subfamily found worldwide in tropical to polar seas. It is well represented in Australian waters, some ischnochitonines being our commonest chiton species. This subfamily is characterised by solid eaves, lack of extra-pigmentary aesthetes, and the girdle scaly.

The Callistoplacinae is a small subfamily found in most temperate to tropical seas of the world, usually in the sublittoral zone. Callistoplacinae are well represented in Australian waters. They are characterised by strong tegmental sculpture of radial ribs on the end valves and lateral areas, solid eaves and lack of extra-pigmentary aesthetes.

The Callochitoninae is another small subfamily, its members found in most seas of the world except the Americas, tropical to polar, usually in the sublittoral zone. The shell is usually covered with a distinct periostracum, which is often brightly coloured in life. Callochitoninae are characterised by the body being oval in shape, with fine granulose tegmentum (sometimes with pleural grooves), porous eaves, presence of extra-pigmentary aesthetes, and small, imbricating, inwardly directed spicules on the girdle.

Chaetopleurinae are small to large chitons The subfamily is well represented in the Northern Hemisphere in tropical to polar seas, but members are also found on the coasts of South America, Africa and Antarctica. The subfamily is not known from the Australasian region; the single species from Australian waters is Nuttallochiton mirandus (Thiele, 1906) from Antarctica. Chaetopleura biarmata Rochebrune, 1882, described from Australia, is now excluded from the Australian fauna (see Pilsbry 1894). Callochitoninae are characterised by pustulose tegmental sculpture, solid eaves, lack of extra-pigmentary aesthetes, and the spiculose or spiny girdle.

Lepidochitoninae are small to medium-sized chitons, and are found mainly in the Northern Hemisphere, in tropical to polar seas. Only two monotypic genera, Subterenochiton and Particulazona, are found in Australian waters. This subfamily is characterised by porous eaves without extra-pigmentary aesthetes, and girdle naked or with non-imbricating scales or spicules.