They were extremely abundant during the Paleozoic Era

, reaching their highest diversity roughly 400 million years ago, during the Devonian Period. At the end of the Paleozoic, however, they were decimated in the mass extinction that marks the end of the Permian Period, about 252 million years ago.

How did brachiopods go extinct?

Besides marking the disappearance of species, the Capitanian was also a time of major volcanic eruptions. Ash from southwestern China's Emeishan Traps, for example, dates to the Capitanian and has previously been implicated as a potential cause of the local brachiopod extinction.

What did brachiopods evolve into?

Palaeozoic dominance

Brachiopods are extremely common fossils throughout the Palaeozoic. ... Before the extinction event, brachiopods were more numerous and diverse than bivalve mollusks. Afterwards, in the Mesozoic, their diversity and numbers were drastically reduced and they were largely replaced by bivalve molluscs.