Brachiopods are equipped with a filamentous feeding tube, which has allowed them to adapt to a great scope of life niches across the seafloor. The lampshells are one of the most diverse and abundant invertebrate phyla, living exclusively in marine environments. First appearing in the early Cambrian, brachiopods continued to diversify and dominate throughout the Paleozoic. Brachiopods range from mere to microns to a half meter in length, with roughly 120 different surviving genera today. They occupy a wide range of habitats over a great spectrum of differing water depths. Most pods, no matter their location, attach similarly onto their respective surfaces by using their arm-like extension pedicles. The pedicle works to cement on a hard substrate or root into soft sediment allowing for attachment. Their ability to cling offers great diversity of brachiopods, where some live in intertidal environments at high latitudes and others basil environments at depths of over 6000m.
Today, the most common settings to find brachiopods are the fjords of Canada, Norway and Scotland and in the ocean surrounding New Zealand as well as the Antarctic. Tropical brachiopods are relatively tiny in size, hiding in reef crevices or corals and sponges, providing optimal resources for food. Alternatively, larger brachiopods prefer living at greater depths of sea level, away from predators.
A variety of brachiopod shell fossils found here in Paleozoic rocks. These fossils are from Virgina's Valley and Ridge Province.
The Lingula anatina brachiopod, here showcasing its long pedicle.
Modern Brachiopods can be found in Fjords such as this from the Appalachian region of Canada.
paleobiogeography
Brachiopods through time have been very successful. Modern faunas have a profound difference then those of Cambrian and Paleozoic origin. The first brachiopods of the Cambrian were mostly dominated by a range of non-articulated groups, such taxa: chileides, obolellides, and pentamerides. These were all members of nearshore, paleocommunities. Diversity greatened during the Ordovician radiation, with new dominant faunas, the deltidiodont orthides and strophomenides. The Ordovician faunas first evolved around island complexes and dominated shelf benthos, finally moving offshore and diversifying around carbonate mounds, forming the basis of the Paleozoic brachiopod fauna.
Brachiopods have experienced five main extinction events, followed by moderate recoveries with different degrees of success. The Ordovician extinction happened in two parts, where background glaciation accounted for the loss of 80% of brachiopod families. The recovery and followed diversity is marked by the loss of deltidiondont groups and the inverse rise of spire-bearing atrypides, and spiriferides with cyrtomatodont dentition. These groups dominated, particularly in carbonate environements. Through the late Devonian period climate change also became influential, and spiriferides and rhynchonellides groups of brachiopods survived. During the Permian there is vast diversity within brachiopods, some are mimicking corals with fantastic spiney displays and others have reduced their shells, exposing soft tissues. The end-Permian extinction accounted for a 90% loss of brachiopod species, and disaster taxa such as lingulids now dominated the brachiopods. Shortly, rhynchonellides and terebratulides became the dominant brachiopods. The end-triassic extinction got rid of most remaining spiriferides and strophonmenides, and again the rhynchonellides and terebratulides brachiopods remained dominant. Lastly, the end-Cretaceous extinction may have caused the loss of 70% of chalk brachiopods in northwest Europe. Despite many declines of phylum, especially felt after the Permian, modern brachiopods are incredibly diverse in their adaptions.
Cambrian brachiopods lived in either tropical or polar realms, while linguliformeans developed widespread distributions in slope settings. During the Triassic, faunas became organized into boreal and tethyan realms, representing high and low latitude respecitively. This pattern followed throughout the Mesozoic, with slight alterations due to ocean currents and local developments within the environment.
Stratigraphic distrubution of brachiopods through time