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Family  Chitonidae

True Chitons

The Chitonidae is a numerically large family of chitons, ranging in size from small to very large. They are widespread in temperate and tropical seas and are well represented in Australia. The family is divided into 3 subfamilies, based on the positions of aesthetes - the minute light-sensitive organs on the shell surface - and the characters of the shell insertion plates. The insertion plates are pectinate througout the family. In the subfamily Chitoninae the valves do not have aesthetes and the girdle has closely-packed smooth or striated scales. In the subfamily Acanthopleurinae the aesthetes occur on the anterior part of the lateral area of the intermediate valves and the girdle is large and covered with a dense arrangement of spikes, spines or scales. In the subfamily Toniciinae, aesthetes are usually numerous and occur on all the valves, and the girdle bears microscopic scales and spicules.

In NSW, most species belong in the subfamily Chitoninae, with a densely scaled girdle, and one species each is placed in Acanthopleurinae and Toniciinae. They are among the largest and most obvious molluscs on the shore, particularly Liolophura gaimardi, which is common on exposed rocky shores, although usually with an eroded shell.

Family References

• Iredale, T. & Basset Hull, A.F. 1927 Family Chitonidae. Pp 104-134 in A Monograph of the Australian Loricates. Royal Zoological Society of New South Wales, Sydney. 168 pp. (This is a consolidated and repaginated version of the same material that was published in sections in The Australian Zoologist over the years 1923-1927).

• Kaas, P. & Van Belle, R., & Strack. H,L. 2006. Family Chitonidae (Reeve, 1847) p. 71-396 in Monograph of Living Chitons Volume 6 E.J. Brill/Dr. W. Backhuys Leiden.

• Gowlett-Holmes, K. 1998. Family Chitonidae. Pp. 185-188 in Beesley, P.L., Ross, G.J.B. & Wells, A. (eds) Mollusca: The Southern Synthesis. Fauna of Australia. Vol. 5. CSIRO Publishing, Melbourne. Part B. viii 565-1234 pp.

• Gowlett-Holmes, K. 2001. Chitonidae. Pp 31-43 in Wells, A. & Houston, W.W.K. (eds) Zoological catalogue of Australia. Vol. 17.2 Mollusca: Aplacophora, Polyplacophora, Scaphopoda, Cephalopoda. Melbourne: CSIRO Publishing, Australia.

Coverage

All the NSW species of the family are detailed here.

Identification Notes

As the characters that place animals into the Chitonidae are minute and internal, dissection and microscopic examination is required for fundamental identification. But the animals are large and distinctive thus enabling recognition of the species on sight.

The descriptive terminology for chitons is given in the introduction to the Acanthochitonidae.