Changes in the communities of Paleozoic brachiopods due to their development of their filtering system

Onward changes in the communities of Paleozoic articulated brachiopods were mainly connected with the improvement of the function of their filter feeding system, which is responsible for the feeding of animals. Three major routes of improvement are known: (1) feeding using a primitive lophophore and specialized mantle (orders Strophomenida, Chonetida, and Productida); (2) increased complexity and enlargement of the spirolophe and the appearance of the spiral brachidium (orders Atrypida, Spiriferida, and Athyridida); (3) development of the protective structures preventing ingestible particles into the inner cavity of the shell (order Rhynchonellida). The most effective was the third variant that allowed rhynchonellids, which appeared in the Ordovician, to live up to recently and survive after two largest extinctions in the history of the group development: in the Late Devonian and at the Permian-Triassic boundary.