Brachiopod

Brachiopods filter plankton, using a specialized organ: the lophophore. It is exceptional to find silicified skeletons of this organ. You can see it in this specimen of Liospiriferina from the Jurassic

Platystrophia ponderosa (Ordovician). Scale bar is 5.0 mm.

Brachiopods with beak-shaped hinges, from the Philippines

Upper Ordovician brachiopod

Brachiopods are a phylum of small marine shellfish, sometimes called lampshells. They are not common today, but in the Palaeozoic they were one of the most common types. They lived near the shore (littoral zone), but now they have been pushed into deeper water by competition from bivalve molluscs. They do look rather like bivalves, but their internal organisation is quite different.

Brachiopods have a huge fossil record going back to the Cambrian. They were much reduced by the two main extinction events, the P/Tr and K/T. Bivalve molluscs took over their inshore habitats in the Mesozoic, and since then the brachiopods have been confined to deeper water, except for a handful of species. There are about 100 to 350 species living; the fossil species number 12,000.