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Family  Ischnochitonidae

Ischnochitonid chitons




The Ischnochitonidae is a very large family of small to medium sized chitons occurring in tropical, temperate and polar seas. They live from the littoral zone down to at least 100 m. The family is particularly well represented in southern Australia; some species, such as Ischnochiton australis, are among the most common animals on intertidal rocky shores there.

The feeding preferences of the Ischnochitonidae are varied. Kangas & Shephed (1984) found herbivorous, omnivorous and carnivorous species in South Australia. Reproductive strategies are also varied. Most species cast eggs and sperm into the sea, but brooding of young in the pallial groove has been reported for several species (Penprase, 1981).


Family References

  • Iredale, T. & Basset Hull, A.F. 1927 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 had been published in sections in The Australian Zoologist over the years 1923-1927).

  • Kaas, P. & Van Belle, R. 1985. Monograph of Living Chitons Volume 2 Suborder Ischnochitonina E.J. Brill/Dr. W. Backhuys Leiden.

  • Gowlett-Holmes, K. 1998. Family Ischnochitonidae. Pp. 180-182 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. Ischnochitonidae. Pp 57-70 in Wells, A. & Houston, W.W.K. (eds) Zoological catalogue of Australia. Vol. 17.2 Mollusca: Aplacophora, Polyplacophora, Scaphopoda, Cephalopoda. Melbourne: CSIRO Publishing, Australia.


All the species of this family known to occur in NSW are treated in detail here, with the exception of the following three problematic species.

Ischnochiton carinulatus (Reeve, 1847)

This was previously known as Ischnochiton tateanus Bednall, 1897, and recorded from SA and Vic. It was reported from southern NSW in 1927 as dredged in Disaster Bay and Twofold Bay (Iredale & Hull, 1927, p. 19), but has never been reported from NSW subsequently.

Ischnochiton purus Sykes, 1896

This is a small, rare subtidal species known from SA and Vic. Iredale & Hull (1927, p. 39) gave the distribution as southern NSW and Victoria but did not give specific localities. The Australian Museum does not hold any specimens from NSW and there are no literature references after 1927 to its occurrence in NSW.

Ischnochiton cariosus Carpenter, 1879

The Australian Museum holds specimens collected by SCUBA from Twofold Bay, NSW, in 1985, which extend the recognised range of WA to Vic into southern NSW.

Identification Notes

The following tabulation shows the girdle scale characters of the subgenera of Ischnochiton.

Ischnochiton (Ischnochiton)

Distinguishing characters: Girdle scales striate

NSW species:

Small scales Ischnochiton examinandus

Medium size scales Ischnochiton elongatus  

 Large scales Ischnochiton versicolor

Ischnochiton (Haploplax)

Distinguishing character: Girdle scales smooth, Valve surface smooth.

NSW species:

 Ischnochiton lentininosus

Ischnochiton smaragdinus

Ischnochiton (Ischnoradsia)

Distinguishing characters: Shell very large size, constant dark color, girdle scales smooth, pointed at sides

NSW species:

Ischnochiton australis

Ischnochiton (Heterozona)

Distinguishing characters: Girdle scales vary in size from large near the valves to small at outer edge of girdle

NSW species:

Ischnochiton fruticosus


Distinguishing character: Shell very small, Valve sculpture shows lines of pustules

NSW species:

Subterenochiton gabrieli


Copyright Des Beechey 2019