Brachiopods, also known as lamp shells, are marine invertebrates that possess two shells enclosing their bodily organs. These creatures have existed for over 500 million years and are considered some of the earliest complex organisms to have inhabited the sea. There are many synonyms for the word "brachiopods," including spiral shells, terebratulid, and rhynchonelliform. Other synonyms for the word include inarticulate brachiopods, articulate brachiopods, and living fossils. Furthermore, some of the more common names used are thumb sea lady, palm shells, and shellfish. Despite having various names, brachiopods remain some of the most intriguing organisms within the animal kingdom.