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Phylum Arthropoda | Class Merostomata | Order Xiphosura > Family Limulidae
Mangrove horseshoe crab
Carcinoscorpius rotundicauda
Family Limulidae
updated Nov 2019
Where seen? This is the smaller of our horseshoe crabs. It is sometimes encountered in our northern shores, in mudflats, mangroves and shores nearby.

Features: Diameter to about 15cm. The circular shell is brownish. Identified by shorter spines on the side of the body, the tail is circular in cross-section near where it joins the body, without a groove on the underside and without spines on the upperside. The male's special legs for holding on to the female has two 'fingers'.

The underside is sometimes encrusted with Flat slipper snails (Crepidula walshi) and bryozoans.

Sometimes confused with the Coastal horseshoe crab (Tachypleus gigas). More on how to tell them apart.

Status and threats: This horseshoe crab is listed as 'Vulnerable' in the Red List of threatened animals of Singapore. According to the Singapore Red Data Book: "It is still relatively common in intact mangroves, and should survive as long as there are enough such habitats conserved."

Using its tail to flip over to the right side
Changi, Jun 05

Spines on the side of the body shorter.

Tail near the body is circular in cross-section
and smooth on the upperside.

Male's special legs for holding onto the female
has two 'fingers'.

Tail without a groove on the underside.

Juvenile horseshoe crab.
Kranji, Jun 08

Mangrove horseshoe crabs on Singapore shores
On wildsingapore flickr

Other sightings on Singapore shores

Sembawang Beach, Sep 20
Photo shared by Marcus Ng on facebook.

Pasir Ris Park, Dec 08
Photo shared by Loh Kok Sheng on facebook.

Pulau Sudong, Dec 09
Photo shared by Ivan Kwan on his flickr.

Pasir Ris Park, Mar 18

Mangrove horseshoe crabs (Carcinoscorpius rotundicauda)


  • 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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