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Acanthopleura gemmata (Family Chitonidae)

Northern Spined Chiton


The Jewelled Chiton has an Indo-West Pacific distribution. In Northern Australia it ranges from Shark Bay, central WA, across NT shores to the Townsville region of north-eastern Qld (WA, NT, QLD).


This large, coarse, round-backed but slightly flattened chiton is variable in shape and height. It grows to a length of 80 to 100 mm. It has distinctive long calcareous spines on the girdle.

It has a shell sculpture consists of blister-like bumps, referred to as being pustulose. The front and rear valves have multiple slits, while the middle valve has one slit. The shell valves have well-developed insertion plates with comb-like teeth that hold the adjacent valves together. Each intermediate valve has a beak-shaped hump. The plates are covered by a greyish-green to greyish-brown covering called a tegmentum, that is usually eroded. There are black marks on the jugium (valve peak). The wide and thick, spined girdle is banded black and white. The girdle is covered with dark brown, grey or black spines that can be straight or curved, pointed or blunt, but are usually conical. In between the taller spines are much smaller spinelets.

Ecology/Way of Life:

The Jewelled Chiton seems to be confined to the intertidal areas and just below to 2 metres, on northern Australian shores. It occurs at high-tide levels and below in crevices or exposed on rocks. It is an algae-feeding herbivore.

Interaction with Humans/Threats:

The jewelled Chiton is common throughout its range, so does not appear to be under any threat from human interaction.

Other Comments:

Acanthopleura gemmata, Blainville, 1825. Acanthopleura comes from two Greek words, acanth comes from akantha (Gr.) = prickle, and pleura comes from pleura / pleuron (Gr.) = rib or side. Gemmata comes from gemma (L.) = a bud.

Further Reading:

Davey, K. (1998) A Photographic Guide to Seashore Life of Australia p.70. New Holland Press, Sydney.

Wells, F.E. & Bryce, C.W. (1988) Seashells of Western Australia. p.30, Western Australian Museum.


Text, map & photograph by Keith Davey.

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