Ammonites are perhaps the most widely known fossil, possessing the typically ribbed spiral-form shell as pictured above. These creatures lived in the seas between 240 - 65 million years ago, when they became extinct along with the dinosaurs.
Ammonite amirugumi, pattern by Lilli Tupilli for sale on Ravelry. "There are two versions given in the pattern: For a fast-growing ammonite and for a slow-growing one. Tentacles are optional. The ammonite is worked in Tunisian crochet, with short rows. These stitches are based on the Tunisian Simple Stitch. They are also known as linked stitches. Pattern has picture tutorials for all stitches and techniques." Do peruse the Project photos for yarn ideas!