Macrophthalmus crassipes is a species of sentinel crab in the family Macrophthalmidae, found around China, Thailand, Malaysia, Australia, and the Caroline Islands.

[1] Common names include the seagrass sentinel crab[2] and the orange spined sentinel crab.

On adult males there is a substantial tooth on the lower claw and a much smaller tooth on the upper claw, and noticeable orange spines on the “wrist” (carpus) of the clawed leg and on the palm of the clawed leg.

[1] The carapace is covered in small granules, and is up to around 37 mm (1.5 in) across.

[3][4] It is a burrowing crab, and lives in open tidal flats, muddy or with sandy mud, low on tidal creek banks, and adjacent mangroves.