Myzostoma (lit. "sucking mouth") is an amphibious clade of Tentaclostoma.
Myzostoma is a sister clade of Lophostoma, descending from the first Tentaclostomes to invade land but never making the full transition to land. As a result, Myzostoma can venture onto land for short periods, but must return to the water to breed and avoid desiccation.
Most species of Myzostomes are omnivorous if not herbivorous, living in freshwater river beds and mud banks. Aside from the change in lifestyle, Myzostomes have no obvious anatomical differences from early Tentaclostomes. They are among the smaller creatures yet observed, measuring only about 2cm in height.