No one knows for sure how many kinds of staghorn corals there are, but scientists estimate there may be nearly 400 species. And only scientists can tell them apart; these corals grow in a confusing variety of shapes and colors. A single small reef may have hundreds of Acropora colonies growing on it. But in all their variety—from flat platelike colonies to pillowlike clumps to the branching, antlerlike form from which they get their common name—these fast-growing corals are consummate reef builders and important members of coral reef communities around the world.