Mytiloida is a suborder of saltwater clams, marine bivalve mollusks, commonly known as mussels. There is one extant superfamily, the Mytiloidea, with a single family, the Mytilidae.Species in the order Mytiloida are found world-wide, but they are more abundant in colder seas, where they often form uninterrupted beds on rocky shores in the intertidal zone and the shallow subtidal. The subfamily Bathymodiolinae is found in deep-sea habitats.Mytilids include the well-known edible sea mussels.