The first animal reefs
Archaeocyath sponges build the first skeletal reefs, and shallow seas gain three-dimensional structure.
- When
- Known to
- ± 3 million years
- Era
- Cambrian, Paleozoic
Archaeocyaths — cup-shaped calcareous sponges — begin constructing reefs on the Siberian Platform around 525 million years ago. They are the first animals to build large rigid frameworks, creating habitat for everything else. Reef size and community complexity increase sharply during an oxygenation pulse at 521 to 519 million years, tying the physical structure of the seafloor directly to ocean chemistry.