Isthminia

Isthminia (named after the Republic of Panama and its people) is a genus of medium-sized river dolphin cetaceans that lived during the Late Miocene epoch in what is now the coasts of Panama, about 6.1 million to 5.8 million years ago. The type species is I. panamensis, known from the littoral Chagres Formation.

Description
Fossils of Isthminia were found in the Chagres Formation in Panama. On the basis of the fossil material, including a partial skull, the length of Isthminia is estimated to be about 2.85 m long. Isthminia probably had a predominantly marine lifestyle.