Gastropods

Euomphalus northi, from the Lower Devonian of Lilydale, Victoria. Source: Museum Victoria.

Gastropods are molluscs. They include a great variety of snails and slugs, and live in the sea, in fresh-water, and on land.

Many gastropods have coiled shells, into which the soft parts of the animal can be withdrawn when danger threatens, and which can then be sealed with a lid (operculum). Gastropods have a head, with eyes, tentacles and a mouth with a rasping lower jaw, and a large flat mucus-covered 'foot' on which the animal slowly slides.

Most snails are hermaphroditic (having male and female organs), but they still mate with each other. Some gastropods are carnivorous, others herbivorous, and others eat decayed matter. Those that live in the water have gills, while land dwellers have lungs.

Euomphalus northi, from the Lower Devonian of Lilydale, Victoria. Source: Museum Victoria.

Gastropods arose early in the Cambrian Period (490 to 545 million years ago), and became very diverse in the Carboniferous Period (298 to 354 million years ago). They were much affected by the mass extinctions at the end of the Permian Period (251 million years ago), but some species managed to survive, and to start to diversify again. From the beginning of the Tertiary Sub-era (65 million years ago) to the present, gastropods have come to dominate many of the environments in which they live. They are probably more numerous now than ever before.

Fossil gastropods are found in various parts of Victoria, including Torquay and Mornington.

Gastropod Ternivoluta antiscalaris, from the Miocene of Victoria. Source: Museum Victoria.

Gastropod Umbilia eximia, from the Miocene of Victoria. Source: Unknown.

Gastropod Umbilia eximia, from the Miocene of Victoria. Source: Museum Victoria.