Ammonite

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Ammonite!

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The ammonites were a group of extinct shelled mollusks that have produced famous fossil specimens. Though they greatly resemble the modern nautilus, they are not very closely related. Their iconic shell spiral fits the pattern of the golden ratio.

The first ammonites appeared during the Devonian period, while the last ammonite died around the Cretaceous-Paleogene extinction event. Some ammonites were bioluminescent.