planispirals
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planispirals |
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| navigate by keyword : ammonites amoniti form forms fossil fossile fossiles fossils gelogical genus geologic geological helically heteromorphs layer marine marines mineral minerals nature natures nonspiraled ocean oceans planispirals prehistoric rock rocks sea seas shell shells species spiral spiraled spirals water waters |
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| Ammonites are excellent index fossils, and it is often possible to link the rock layer in which a particular species or genus is found to specific geological time periods. Their fossil shells usually take the form of planispirals, although there were some helically spiraled and nonspiraled forms (known as heteromorphs). |
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Stockphotos.ro (c) 2025. All stock photos are provided by Dreamstime and are copyrighted by their respective owners. |
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