Bryozoans and crinoids take over the seafloor
Filter feeders on stalks and in colonies carpet the shallow seas, creating a forest of animals.
- When
- Known to
- ± 5 million years
- Era
- Ordovician, Paleozoic
Bryozoans — colonial animals building lace-like and branching skeletons — appear at the start of the Ordovician and radiate spectacularly. Crinoids, echinoderms mounted on long stalks, form dense meadows that give the seafloor vertical structure for the first time. Together with brachiopods they define the Paleozoic evolutionary fauna, an assemblage that dominates marine life until the Permian.