Pictured here is the exterior, dorsal valve. Also, growth lines that cross the plicae are evident in this photo. The brachiopods of the Phylum Brachiopoda are by far the most diverse and abundant of all the skeletonized invertebrates of the Paleozoic. There are approximately 300 species that exist today and over 30,000 are evident in the fossil record. Brachiopods had many different body forms and occupied many different niches throughout the seafloor.
Brachiopods are entirely marine.
Brachiopods were once again very common in the Paleozoic, but became extinct in the Permian. Characteristic of the brachiopods are two valves with one usually being slightly larger than the other. Brachiopods bear adductor and diductor muscles that help them open and close their shells. The top valve on the brachiopod is considered the dorsal valve and the ventral valve would be the bottom valve, which sticks out slightly toward the posterior. Brachiopods were solitary, sessile, and benthic.