There are many limpets in the Paleozoic fossil record, from the lower Cambrian, but none can be placed with certainty in the Patellogastropoda. Some might be Monoplacophorans, which is a separate mollusc class with a similar life-style. The earliest patellogastropod verified by shell microstructure is from the Triassic of Italy, but it is in the Upper Cretaceous and Cainozoic periods that many of the living forms make their first appearance.