Scientists have recently found a 260-million-years old fossil of a weasel-sized prehistoric reptile from Russia that had the first modern ears:
Paleobiologists uncovered large-eyed fossils of these reptiles with surprisingly advanced ears near the Mezen River in central Russia. They are a kind of now-extinct reptile called a parareptile.
The outside of the cheek in the reptiles was covered with a large eardrum. This structure was connected with the inner ear and the brain with a bone comparable to those in human ears.