Lingulata's a class of brachiopod, among the oldest of all brachiopods having existed since the Cambrian period (550 mya). They're also among the most morphologically conservative of the brachiopods, having lasted from their earliest appearance to the present with very little change in shape. Shells of living specimens found today in the waters around Japan are almost identical to ancient Cambrian fossils. The Lingulata have tongue-shaped shells (hence the name Lingulata, from the Latin word fo… (More on Lingulata)