Lingulata Brachiopod

This is a Silurian (430 million year old) lingulata brachiopod shell from Joliet, Illinois (UC 9903). Lingulata brachiopods differ from most other brachiopods by having a shell that is composed of calcium phosphate instead of calcite. Muscles hold their shells together rather than teeth and socket common in other brachiopod shells. Lingulata brachiopods are often cited as a living fossil because living species such as Lingula anatine have shells that look very similar to ancient forms that lived over 530 million years ago (Cambrian Period), giving the impression that this species has not evolved. The shells may look similar because of the animals life style of burrowing into sandy and muddy seafloors, but there are more differences and Lingula brachiopods are not truly living fossils.