The phylum Brachiopoda is divided into two classes, Inarticulata and Articulata.
Brachiopods are benthic, sessile organisms. Some are infaunal and others are epifaunal.
They are filter feeders and use a lophophore to beat the water and create currents bringing
in food. They have exoskeletons made of calcite or aragonite and grow by accretion (Thompson 1997).
Brachiopods were the next most numerous organism to trilobites during the
Cambrian. There were mainly inarticulate brachiopods and some articulate brachiopods.
During the Ordovician, the brachiopods became the most numerous fauna. The shallow, warm
marine environment was also very favourable to their growth and diversification.
Articulate brachiopods became more numerous during this time but inarticulate brachiopods
were still present. Lingula species, an inarticulate brachiopod, can still be found alive
today, although only its fossils are found in Ottawa.