Gastropods are a large group of molluscs. Most have a coiled or conical shell, a muscular foot, eyes, tentacles and a feeding organ or radula. They first appeared in the Cambrian period and colonised all marine habitats. Some lived on the seabed, others burrowed into the mud or sand or attached themselves to rocks. Gastropods thrive in abundance today, inhabiting both aquatic and terrestrial environments and include whelks, garden snails and slugs.
Silurian gastropods were entirely marine.