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Phylum Arthropoda > Subphylum Crustacea > Class Malacostraca > Order Decapoda > Brachyurans > Superfamily Majaoidea
Arrow-head spider crab
Menatheius sp.*

Family Epialtidae
updated Dec 12

Where seen? This tiny crab is sometimes seen on some of our shores, among seagrasses and seaweeds. It is probably quite common but overlooked because it is so well camouflaged.

Features: Body width 0.5-1cm. Body rather flat and quite triangular with a sharp pointed tip between the eyes. Walking legs and pincers long. May be brown or green. Slow moving.

According to the Singapore Red Data Book, the One-horned spider crab (Menaethius monoceros) is found among seaweeds such as Sargassum, and among seagrasses on rocky or sandy/muddy shores. It also covers itself with debris to blend into the surroundings.

Labrador, Jun 05

Terumbu Selegie, Jun 11
Photo shared byJames Koh on his blog.

Tanah Merah, Jul 09
Photo shared by Toh Chay Hoon on her blog.

Chek Jawa, Jan 02

*Species are difficult to positively identify without close examination.
On this website, they are grouped by external features for convenience of display.

Arrow-head spider crabs on Singapore shores

Photos of Arrow-head spider crabs for free download from wildsingapore flickr

Distribution in Singapore on this wildsingapore flickr map

  • Ng, Peter K. L. and Daniele Guinot and Peter J. F. Davie, 2008. Systema Brachyurorum: Part 1. An annotated checklist of extant Brachyuran crabs of the world. The Raffles Bulletin of Zoology. Supplement No. 17, 31 Jan 2008. 286 pp.
  • 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.
  • Lim, S., P. Ng, L. Tan, & W. Y. Chin, 1994. Rhythm of the Sea: The Life and Times of Labrador Beach. Division of Biology, School of Science, Nanyang Technological University & Department of Zoology, the National University of Singapore. 160 pp.
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