Rugosa (solitary), gen. indet.

A solitary rugose coral — a horn coral. Unlike modern reef corals, which are almost all colonial, many rugosans lived alone, and grew far larger than any single living coral polyp could.

The animal sat with the pointed tip of its cone shallowly buried in sea floor sediment. Strong currents occasionally toppled them, and the coral then resumed building towards the new upward direction — which is why so many horn corals are bent rather than straight.

Rugose corals are named for the wrinkled outer wall. They are, like the tabulates, an exclusively Palaeozoic group; both were wiped out at the end of the Permian and modern corals are not their descendants.