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Gastropods
The gastropods (Gastropoda) include snails and whelks as well as limpets. Their large, sole-like foot is used to move them around. Snails are terrestrial, while limpets, whelks, and the like, live in shallow seas.
The shell is usually a conical, spiral shape.
It has no divisions (which distinguishes it from ammonites). Some gastropods have coiled shells, others have straight shells. Coiled gastropods
are very varied and are used for identifying Tertiary rocks.
Gastropods first developed in Palaeozoic times, but remained uncommon throughout this era and even throughout much of the Mesozoic Era. They are very distinctive in some beds, however, and very common in, for example, the Jurassic ‘marble rocks’. Gastropods were most abundant in the Tertiary Period.
Spiral angle
Recognising gastropods
Gastropods have a single shell. Many have a spiral whorl, making them snail-like to look at. However, many others do not have a whorled shape. The only other coiled fossil is an ammonite. Whorled gastropods have a single whorl with no walls between chambers, whereas ammonites have a spiral shell with many chambers. This is the easiest way to distinguish gastropods from ammonites.
Whorl
Hard shell is preserved.
Siphon
Soft parts not preserved
(Below) Turitella of Eocene age.
Eyes
Operculum
Foot
Aperture
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