Gastropods (formally, Gastropoda) make up a large group (class) of molluscs. They have a muscular foot, eyes, tentacles and a special rasp-like feeding organ called the radula, which is composed of many tiny teeth. Most gastropods have a coiled or conical shell, which may be extremely reduced in some species or lost entirely as in slugs. 

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Gastropods evolved early in the Cambrian, but since the Palaeogene they have become the most common molluscs, inhabiting both aquatic and terrestrial environments.