Acanthastrea / Micromussa is a genus of large polyp stony corals in the family Lobophylliidae. The colonies are massive and usually flat. The corallites are either circular or angular in shape. The septa are thick near the wall of the corallite, becoming thin near the columella, and have tall teeth. The polyps are extended only at night. They come in beautiful vibrant colours and come in a range of sizes.