Brachiopoda
Phylum Brachiopoda, often known as "lamp shells", are a phylum of animals that have hard "valves" (shells) on the upper and lower surfaces, unlike the left and right arrangement in bivalve molluscs. Brachiopod valves are hinged at the rear end, while the front can be opened for feeding or closed for protection.
About Brachiopoda
Brachiopods live only in the sea. Although superficially resembling bivalves, brachiopods are not closely related, and evolved their two valved structure independently, an example of convergent evolution. There are around 400 living species of brachiopods living mainly in cold water and low light conditions and range in size from 1 mm to over 90mm, most species are between 10mm and 30 mm in length.
Most shell collectors do not collect Brachiopoda shells as they are not Mollusca, however, their popularity is increasing. Fossil Brachiopoda are popular with fossil collectors, there being a greater species diversity amongst the fossils.
Brachiopoda are first seen in the fossil record in the early Cambrian period, approximately 541 million years ago. They were very abundant throughout the Paleozoic Era and are often found as fossils in rocks from that time.