When a Lutellaria died, its shell often landed in a calm, low-energy lagoon. Here, fine carbonate mud (calcareous ooze) buried the shell rapidly. This prevented scavengers from breaking it apart and, crucially, preserved the delicate hinge and inner tooth structures.
These bivalves were burrowers. They used a powerful muscular foot to dig into the seafloor, leaving only their siphons exposed to filter plankton. Their extinction at the end of the Eocene is likely linked to the global cooling event known as the Eocene-Oligocene transition, which caused sea levels to drop and disrupted their shallow-water habitats. As they died out, their shells accumulated in massive, dense beds—what geologists call coquina. seal of lutellaria
Even knowing their origin, scientists agree that late Stone Age cultures intentionally collected and used these fossils as sealing devices. Why? When a Lutellaria died, its shell often landed