Pellet-Lined Burrow (Ophiomorpha)

This fossilized crustacean burrow is lined with the pellets created by its former inhabitant. While some think these are fecal pellets, it is more likely lined with creations closer to spit balls. The pellets are more gritty/granular than coprolites. Plus, crustacean fecal pellets are more rod-shaped. Some modern day crabs and ghost shrimp still use this construction method.