How old is the world's oldest seashell?

Answer 1

There are seashell fossils that are 65 million years old. They are found in areas that were once covered by ancient seas/oceans. I live in an area of CA where if you go to the right place you can find them plus ancient shark teeth.

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In fact fossil shells far older than that are common, if not necessarily in California. That 65Ma marks the end of the Creataceous and prior to the that the Jurassic, both rich in life now represented by fossils. Limestones from The Carboniferous (represented in the US by e.g. the Pennsylvanian) , hold fossil corals and shells from well over 300Ma; but the oldest significant fossils of sea creatures are of Cambrian age..

Answer 2

The world's oldest seashell is estimated to be around 500 million years old. These seashells are preserved in ancient rock layers and provide important information about Earth's history and past environments.