Phylum brachiopoda includes the shelly marine fauna that were once exceptionally abundant through most of life's history on earth, however are rarely found today. Unlike bivalves, both halves of brachiopod shells are not identical. Instead the bottom half (pedicle valve) tends to be more 'cup-shaped' and the top half (brachial valve) acts as a lid. Brachiopods filter feed with a specialized organ called a lophophore. They inhabit a range of environments from shallow to deep and while most attach to a hard substrate incapable of moving, lingulid brachiopods burrow into the sediment.