There is a pervasive attitude that reels were isolated from the mainstream of evolution and that their history had quite a different pattern from the level-bottom marine biota. However, three striking similarities exist between the evolution of reefs and other marine communities. (1) Reef composition and ecologic structure were governed by the composition of the three Phanerozoic evolutionary faunas. (2) Reefs were decimated by the major extinction events of the geologic record. (3) Reefs conform to the pattern of level-bottom community evolution. Intervals when reefs were absent were due either to the absence of appropriate frame-building organisms in the biota (for example in the Middle and Late Cambrian) or to the absence of reefs following extinction events before frame-building organisms re-evolved a reef-building mode of life.