Characters: Colonies are irregular clumps or corymbose plates with thick branches of highly irregular length and shape. Branches may be tapered (in wave washed habitats), conical, dome-shaped or globular (in less exposed habitats), depending on the degree of formation of axial corallites. One or more axial corallites may occur on branch ends or, commonly, there are no axial corallites. Radial corallites are irregularly immersed to tubular and often have slit-like openings and pointed rims, giving colonies a spiny appearance. Colour: Cream or brown. Similar species: Acropora polystoma, which has well defined axial corallites, does not form dome-shaped or globular branches and has less irregular radial corallites. See also A. lutkeni. Habitat: Upper reef slopes, especially those exposed to strong wave action. Abundance: Uncommon