The buoyancy organ of the Spirula spirula, found on the beaches of Fuerteventura, is the model for this ring.
Spirula spirula is the only living species of the spirulid order. They live in deep water and are therefore rare; however, their very light and resistant inner shell is very common on beaches. The oldest representatives of the group are known from the Carboniferous (about 360-300 million years ago).
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Silver 925/000