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A short glossary of some terms used in Gastropods Through The Ages. Scroll down to search for the meaning for your word. Hit the BACK button in your browser button bar to go back to the page you were at before.

Aestivation - the state of dormancy some gastropods undertake to escape especially dry or hot periods; this may last up to 6 years in some desert species, with no intake of food or water.

Aragonite - a form of calcium carbonate that most molluscs make their shells out of. It has a tendancy to break down more easily during fossilisation than regular calcium carbonate.

Amphineura - 'Chitons.' A class of the Phylum Mollusca that are marine, bilaterally symmetrical and have a chitinous shell (like an insect's).

Aplacophora - 'Soleonogasters.' A class of the Phylum Mollusca. Wormlike and marine, living in deep water ooze.

Archimollusc - a hypothetical ancestral mollusc from the Cambrian, in which all the basic structures of today's molluscs are present, though not specialized.

Calcium Carbonate - CaCO3. The material a gastropod's shell is made up of. Ca and CO3 ions are taken up out of water in the snail's environment, and put together by the snail's mantle lining, where it crystallizes into CaCO3 and adds to the shell.

Cephalopoda - a class of the Phylum Mollusca. Includes squids, octopi, cuttlefish, nautiloids, and extinct ammonites and belemnites. Generally the most advanced of all molluscs.

Chloroplast - an organelle in plant and algea cells that absorbs solar energy and converts it to chemical energy for the plant.

Epiphragm - a mucous membrane secreted by some pulmonate gastropods over the aperture of the shell, which hardens and forms an impermeable barrier. Used to seal the snail in it's shell and prevent moisture loss during aesitvation.

Gastropoda - the snails and slugs. A class of the invertebrate Phylum Mollusca. Assymetrical torsioned bodies with well developed head and a broad foot; shell of one piece often coiled in a helical spiral (though in the slugs the shell is missing). Live in terrestrial, marine and freshwater habitats in a great diversity of forms.

Hermaphroditic - wherein species members are both male and female in the same individual.

Mantle - a thin layer of cells just below the snail's shell that is responsible for shell formation.

Mantle Cavity - a cavity in the gastropod's body that is open to the outside and contains the gills.

Mollusc - any of a group of unsegmented animals of Kingdom Animalia, with body divisible into a head-foot and visceral mass, the mass covered by a mantle that secretes a calcareous shell. Externally often ciliated and mucous, and having a radula tooth structure.

Monoplacophora - a class of the Phylum Mollusca. Mostly extinct (though 4 species are sitll alive in the deep eastern Pacific) bilaterally symmetrical, with one piece oval shell.

Nudibranch - an order of the opisthobranchs that are made up of sea slugs (without shell), and having external gills. Often carnivorous, free swimming or crawling. Marine.

Operculum - a calcareous 'plug' attached to the foot of some prosobranchs, drawn in behind the snail when it is retreating into it's shell to seal the aperture against predators or moisture loss.

Pteropod - a subgroup of the gastropods, the pteropods are free floating small (<2cm) marine snails that make up some part of oceanic plankton. First appearing in the Tertiary, they make up pteropod ooze often found on the sea floor.

Radula - a belt of serially arranged teeth in a gastropod's mouth, often replaced from the rear as front teeth are worn down.

Scaphopods - 'Tooth-Shells.' Small benthic marine molluscs with tapering curved shells open at both ends.

Septa - internal partitions within a mollusc's shell.

Torsion - a 180° rotation of a gastropod's organs, from posterior to anterior position about the head. Occurs in larval stage.

Trocophore - a small globular aqueous gastropod larva; the first stage of gastropod growth. Most often planktonic (free floating).

Veliger - a small, thin shelled aqueous gastropod larva; the second stage of growth. Pelagic (swimming).

Visceral Hump - or 'visceral mass'. A large "bump" on the gastropod that contains the digestive glands, kidneys, guts, and nervous, cirulatory and muscular systems.


Fossil Record

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