The reefs of the Permian were primarily not coral reefs, nor did they resemble the elaborate and sometimes towering reefs that follow tropical coastlines and encircle Pacific islands. Permian reefs were generally mud mounds of carbonate sludge or reef mounds which incorporated larger skeleton building organisms. (Flugel, 1994) These fossil reefs displayed a zonation similar to those shown today: fore-reef talus, a reef slope, crest, flat and a back-reef lagoon. An example of such a late Permian reef is the Capitan Reef of southwestern Texas and southeastern New Mexico (see right). (Wood, 1998)

During the late Permian, these reefs were in abundance. Then, by the beginning of the Triassic, they were gone. The organisms that created them, the rugose and tabulate corals, fusulinids, echinoderms, bryozoans and brachiopods, disappeared forever. For the following ten million years, the Early Triassic, there were no reefs. This period is known as the Early Triassic Reef Gap.