Both solitary and colonial forms are known, but the former are more common. The skeleton is made of calcite and is generally quite massive. Solitary rugose corals range in size from a few millimeters in diameter and in length to 14 centimeters in diameter and a height of close to one meter. Some colonies may be 4 meters in diameter. The septa radiate out from the center.
Rugose corals have both major and minor septa.
Both solitary and colonial rugosans have this distinctive septal insertion pattern, which gives most rugose corals bilateral symmetry. The six prosepta are added first, including the cardinal septum and counter septum , which are at 180 degrees from one another. . New corallites may bud asexually, although they also reproduced sexually. The buds have four septa. As the corallite grows, the septa begin to spread further apart, and new septa are added, generally, four septa at a time are added to maintain a rigid structure.