Shells of the Chambered Nautilus, Nautilus pompilius (Nautilidae) are formed by two layers. The external layer has a pattern of irregular brown to reddish brown stripes, while the inner layer (as seen in the photo) is striking white iridescent.
The iridescent material inside nautilus shells is sometimes machined into pleasing shapes and sold as “Osmeña pearl.”
Name: Aturia praeziczac
Location: Luxor governorate, Egypt, Esneh Shale
Age: 49-66 million years ago, Paleogene Period (Eocene Epoch)
Again and again, different groups of animals end up with the same shape. The fossil in the photograph is Aturia, a nautiloid. Nautiloids and another group, ammonoids, both have spiral-shaped shells and are commonly confused for one another. Here, the similarity doesn’t stop at the spiral.