Characters: Colonies are cerioid with neat angular corallites up to 8 millimetres diameter. Septa have 1-3 large teeth. Colonies have a thick fleshy mantle usually covered with fine papillae.
Colour: Brick-red or green in northern Japan, grey elsewhere.
Similar Species: Acanthastrea lordhowensis, which has larger, less uniform corallites containing more septa. See also Micromussa minuta.
Habitat: Protected reef environments and rocky foreshores.
Abundance: Uncommon in mainland Japan, rare elsewhere.
Taxonomic Note: May be difficult to separate from other Micromussa.
Taxonomic References: Veron (1990a) as Micromussa amakusensis; Veron (2000a);
Identification Guides: Nishihira and Veron (1995) as Acanthastrea diminuta; Chan, Choi, McCorry et al. (2005); Pichon, Benzoni, Chaineau et al. (2010); Turak and DeVantier (2011b);
