Leptophoca lenis

Leptophoca lenis is recognized from fossils found at the Calvert Cliffs on the Chesapeake Bay in Maryland, in sediments of the Calvert Formation. The cliffs are one of the most famous fossil sites on the American East Coast.

It lived during the Miocene epoch, tens of millions of years ago, with its remains coming from the broadly middle-Miocene deposits exposed along the Calvert Cliffs. That makes it far older than any living seal species.

It is regarded as one of the oldest known true seals, meaning it belongs to the Phocidae, the family that includes all living seals. Fossils like it help document when and how early phocids diversified in the world's oceans during the Miocene.

The Calvert Cliffs are still actively eroding and yielding Miocene fossils, mostly shark teeth but occasionally marine-mammal remains. Fossil collectors visit the public beaches along the cliffs, and finds from the area are displayed at institutions such as the Calvert Marine Museum in Solomons, Maryland.