Coral is the name given to sea-floor dwelling, attached Onidarians (formerly known as Coelenterata) of the class Anthozoa. Corals may be solitary or colonial. Colonial corals create coral reefs. Corals secrete a calcite skeleton that preserves well as a fossil.

Fossil corals are normally divided into two groups:-

• The rugose corals (means having a wrinkled skin) had well developed septa, were both solitary and colonial, and lived from the Ordovician to the Permian.
• Tabulate corals were colonial corals having few skeletal elements. They are confined largely to Palaeozoic rocks.

The Carboniferous Dibunophylum bipartitum, shown in the picture, is a solitary coral from the north of England.