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The Ischnochitonidae is a very large family of small
to medium sized chitons found in tropical, temperate and polar seas.
They occur 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.
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,
Iredale, Tom & 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 London Cologne Copenhagen.
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
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
All the species of this family known to occur in NSW
are treated in detail here, with the exception of the following three
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 not been
reported from NSW since then.
Ischnochiton purus Sykes, 1896
This is a rare, small, 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 Pilsbry, 1892
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.
The following tabulation shows the girdle scale
characters of the subgenera of Ischnochiton.
Distinguishing characters: Girdle scales striate
Ischnochiton examinandus Small scales
Ischnochiton elongatus Medium size scales
Ischnochiton versicolor Large scales
Distinguishing character: Girdle scales smooth,
Valve surface smooth
Distinguishing characters: Shell very large size,
constant dark color, girdle scales smooth, pointed at sides
Distinguishing characters: Girdle scales vary in
size from large near the valves to small at outer edge of girdle
Distinguishing character: Shell very small, Valve
sculpture shows lines of pustules