This is a whale inner ear bone from an ancient whale, one of the favorite foods of the megalodon shark.
It measures 2.5"
These prehistoric sperm whales lived during the Miocene epoch, meaning this fossil is between 5 and 23 million years old, the fossil record indicates that these whales grew up to 60 feet in length.
Based on the fossil record of sperm whales we have learned that they hunted other mammals and could have even preyed on smaller sharks.
Sperm whales were also a key part of the ecosystem supporting the apex predator megalodon. The megalodon shark preyed on the sperm whale, we know this because of the fossil sperm whale bones that have been found with large gashes and marks caused by the megalodon's giant teeth.
Below is a video of a different whale earbone being found in a dark water river. It is not the earbone listed here but gives you an idea of how these fossils are found.