Brachiopods

Brachiopods are thought to have evolved from "tommotiid" ancestors during the Early Cambrian. Brachiopods were highly diverse during the Paleozoic era, when their diversity exceeded that of bivalves. Their diversity was strongly affected by the end-Capitanian and end-Permian mass extinction events, from which their diversity would never recover to its former Paleozoic levels, with bivalves subsequently ascending to dominance in marine ecosystems. Today, there are around 400 living species of brachiopods, in comparison to around 9,200 species of bivalves. Brachiopods now live mainly in cold water and low light.