First coral-like organisms appear
Early anthozoan ancestors emerge in Precambrian seas, laying groundwork for reef-building life.
Rise of the first true reef-building corals
Scleractinian and tabulate corals begin forming the earliest true reef structures in tropical seas.
Devonian reef ecosystems flourish
Massive reef systems built by tabulate and rugose corals dominate warm shallow seas worldwide.
Permian mass extinction devastates reef life
The Great Dying wipes out most reef-building corals and countless marine species.
Modern scleractinian corals diversify
Stony corals radiate across Triassic and Jurassic seas, forming the ancestors of today's reefs.
Great Barrier Reef begins forming
The world's largest coral reef system starts developing off the coast of northeastern Australia.
Indo-Pacific coral triangle reaches peak biodiversity
The Coral Triangle region becomes the richest marine biodiversity hotspot on Earth.
European naturalists begin scientific study of coral
Early modern scientists debate whether coral is plant, mineral, or animal.
Charles Darwin publishes theory of coral reef formation
Darwin proposes his influential theory explaining atoll, barrier, and fringing reef formation through subsidence.
Global mass coral bleaching events intensify
Rising ocean temperatures trigger unprecedented worldwide coral bleaching, devastating reef ecosystems.
Diverse reef fauna colonizes coral ecosystems
Fish, mollusks, crustaceans, echinoderms and marine reptiles evolve alongside corals, turning reefs into some of the richest habitats on Earth.
First coral-like organisms appear
Fossil evidence suggests simple soft-bodied cnidarian relatives existed long before true corals evolved, living in shallow ancient seas and forming the evolutionary root of later reef ecosystems. These organisms lacked hard skeletons but represent the earliest steps toward coloniality and calcification that would define reefs.