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Phylum Arthropoda > Subphylum Crustacea > Class Malacostraca > Order Decapoda > Brachyurans
Pebble crabs
Family Leucosiidae
updated Jan 2020

Where seen? These crabs really do resemble tiny pebbles and are sometimes seen on our Northern shores. Silty, sandy areas near seagrasses. They are usually buried under the sand.

Features: Body width 1-2cm. Body smooth somewhat rhomboid, indeed resembling a tiny pebble. The head forms a blunt pointed tip with a pair of tiny eyes. In this way, its eyes can peep out while the rest of the crab is buried underground. It has powerful long flat pincers with pointed claws. The crab can bury itself in the sand very rapidly. Some may be colourful.

Changi, Apr 08

Seulocia vittata
Chek Jawa, Jan 02

Leucosia anatum
Mating pebble crabs
Changi, Jul 05
According to the Singapore Red Data Book, the Rubble crab (Favus granulatus) is known only from Singapore and was a new genus and species discovered from Singapore and is not yet known elsewhere. It was found on Siloso Beach of Sentosa which has since been 'improved', and Pulau Semakau. Alox somphos, a related species in another genus was also first described from Singapore.

Status and threats: Some of our pebble crabs are listed as 'Endangered' on the Red List of threatened animals of Singapore.
Like other creatures of the intertidal zone, they are affected by human activities such as reclamation and pollution. Trampling by careless visitors also have an impact on local populations.

Pebble crabs on Singapore shores
On wildsingapore flickr

Other sightings on Singapore shores

Leucosia anatum

Changi, Jul 08

Leucosia anatum

Changi, May 12

Leucosia anatum

Changi, Jul 12

Changi, Jun 13
Photo shared by Loh Kok Sheng on flickr.

Chek Jawa, Dec 19
Photo shared by Adrianne Lee on facebook.

Tanah Merah Ferry Terminal, Jun 15
Photo shared by Heng Pei Yan on facebook.

East Coast Park, May 21
Photo shared by Loh Kok Sheng on facebook.

Kusu Island, Apr 17
Photo shared by Toh Chay Hoon on facebook.

St John's Island, May 09
Photo shared by Loh Kok Sheng on his blog.

Leucosia craniolaris
Pulau Semakau, Mar 08
Photo shared by Loh Kok Sheng on his blog

Family Leucosiidae recorded for Singapore
from Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore
++from The Biodiversity of Singapore, Lee Kong Chian Natural History Museum.
in red are those listed among the threatened animals of Singapore from 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.
^from WORMS

+Other additions (Singapore Biodiversity Records, etc)

  Family Leucosiidae
  *Alox somphos (EN: Endangered)

Arcania erinacea
Arcania undecimspinosa


Ebalia malefactrix=^Philyra malefactrix
(Mangrove pebble crab)

Favus granulatus
(Rubble crab) (EN: Endangered)

++Heteronucia margaritata/Nucia
aff. mesenensis

Ixa cylindra=^Ixa cylindrus

++Leucosia anatum
Leucosia craniolaris
+Leucosia major
+Leucosia singaporensis

Myra fugax

Nursia malefactrix
Nursia punctata
Nursia tohae

++Oreophorus sp.
Oreophorus rugosus=^Alox rugosum

Pariphiculus coronatus

Philyra heteograna=^Lyphira heterograna
+Philyra malefactrix

Praosia punctata
(EN: Endangered)

++Pseudophilyra sp.
+Pseudophilyra punctulata

++Seulocia crepuscula
+Seulocia cristata
+Seulocia pulchra
+Seulocia vittata
+Seulocia/Urnalana sp.
+Seulocia cf. vittata

With grateful thanks to Ondrej Radosta for identifying the species of the crabs on this page.


  • P. K. L. Ng & H. Komatsu. 29 June 2016. Nursia tohae, a new species of coral rubble mimic crab (Crustacea: Brachyura: Leucosiidae) from the Philippines and Singapore. The Raffles Bulletin of Zoology 2016 Supplement No. 34 (Part I of II) Pp. 519-527.
  • Lee Bee Yan & Martyn E. Y. Low. 21 March 2014. The mangrove pebble crab Philyra malefactrix at Kranji. Singapore Biodiversity Records 2014: 75-76
  • Chen H.-L and Peter K. L. Ng. 2003. On new species of Leucosiidae (Crustacea: Decapoda: Brachyura) from Singapore and the South China Sea. The Raffles Bulletin of Zoology. 51 (1): 61-69
  • 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.
  • Wee Y.C. and Peter K. L. Ng. 1994. A First Look at Biodiversity in Singapore. National Council on the Environment. 163pp.
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