👉 Echinostomes are a group of marine cephalopods that include oars, mussels, and snails. They have a bony shell with a hard exterior and a soft, flexible interior. Echinostomes are known for their ability to move through water and are often found in fresh and saltwater environments. Echinostomes were first discovered during the Paleozoic era (about 430 million years ago) by paleontologist Robert Hutton in his study