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Phylum Echinodermata > Class Echinodea > Order Clypeasteroida
Thick-edged sand dollar
Jacksonaster depressum
Family Laganidae
updated Oct 2016
Where seen? This small sand dollar is seldon seen. Usually on soft silty sand in sheltered lagoons, often only a few individuals. It was previously known as Laganum depressum.

Features: Body diameter 4-6cm. Somewhat pentagonal rather than circular. On the upperside it is thick at the edges with a shallow depression around a raised centre. The thick edge is more obvious in a dead sand dollar. The petalloid is obvious and large even in living sand dollars. Spines at the edges of the body are longer. The underside has long spines, the anus is on the underside. Pale or rose pink, beige or purplish. According to Lane, this is an uncommon species that was only found in trawl hauls in the Southern islands. He also observed some at Pulau Semakau, using their spines to move over soft sediments and not for burrowing.

Status and threats: This sand dollar is listed as 'Vulnerable' on the Red List of threatened animals of Singapore.

East Coast, Nov 08

Thick edge more obvious
in a dead sand dollar.
Seringat-Kias, Jun 09

Underside.

Mouth in the centre.

Thick-edged sand dollars on Singapore shores

Photos of Thick-edged sand dollars for free download from wildsingapore flickr

Distribution in Singapore on this wildsingapore flickr map


Dead sand dollar.
Changi, Apr 10
Photo shared by James Koh on his blog.


Pulau Sekudu, Jun 17
Photo shared by Loh Kok Sheng on facebook.

Pulau Sekudu, Jul 13
Photo shared by Loh Kok Sheng on his blog.

Pulau Sekudu, Jul 16
Photo shared by Loh Kok Sheng on his blog.


Berlayar Creek, Oct 15
Photo shared by Jonathan Tan on facebook.

Berlayar Creek, Oct 17
Photo shared by Marcus Ng on facebook.

Beting Bermban Besar, Nov 14
Photo shared by Loh Kok Sheng on facebook.


Pulau Berkas, May 10

Photo shared by Loh Kok Sheng on his flickr.

Pulau Berkas, May 10

Photo shared by Loh Kok Sheng on his flickr.

Sentosa, May 09

Photos shared by Loh Kok Sheng on his blog.

Links
  • The Echinoid Directory by Dr. Andrew B. Smith on the London Natural History Museum website: everything you could possibly want to know about sand dollars and sea urchins with lots of large close-up images and explanatory diagrams. With technical descriptions and photos of Laganum.
  • Jacksonaster depressum in SeaLife Base: Technical fact sheet.
References
  • Lane, David J.W. and Didier Vandenspiegel. 2003. A Guide to Sea Stars and Other Echinoderms of Singapore. Singapore Science Centre. 187pp.
  • Davison, G.W. H. and P. K. L. Ng and Ho Hua Chew, 2008. The Singapore Red Data Book: Threatened plants and animals of Singapore. Nature Society (Singapore). 285 pp.
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