Characters: Colonies consist of flat, highly fused, basal branches with irregular upright branchlets. Colonies may be over 2 metres across and can sometimes form a single solid plate. Axial corallites are tubular and distinct. Radial corallites are immersed on older parts of colonies, becoming tubular with nariform openings on peripheral parts. Colour: Dark brown or green. Similar species: Acropora natalensis and A. branchi. See also A. glauca, which has a similar growth-form but has rounded peripheral corallites and indistinct axial corallites. Acropora divaricata and A. stoddarti may have similar corallites; the former seldom forms flat plates, the latter always does. Colonies in some exposed habitats resemble A. irregularis. Habitat: Shallow reef environments and rocky foreshores in subtropical locations. Abundance: Common at subtropical locations, rare elsewhere.