Nautiloid overview.
Coiled nautiloids are related to the Straight-shelled nautiloids, but instead of a straight shell, they bare a resemblance to their descendants, the Cretaceous ammonite. They appear in Death rays.
Death rays
Initially, they are seen trying to find some food. Once the extinction occurs, their eggs are killed due to the intense radiation. These nautiloids do better then their cousins the straight-shelled nautiloids, because of their coiled shell being stronger and more resistant to pressures. They manage to survive, and eventually evolve into the Cretaceous ammonites.
Trivia The nautiloids are perhaps Aphetoceras, which were present in the end-Ordovician. However, Aphetoceras' shell is much less coiled than the nautiloid shown here.