Isthminia panamensis

Isthminia panamensis is an extinct river dolphin and the type species of the genus Isthminia. It lived during the Late Miocene epoch, roughly 6.1 million to 5.8 million years ago, in waters off what is now the coast of Panama, and it is known from fossils found in the littoral Chagres Formation, including a partial skull. From that material, the animal is estimated to have been about 2.85 metres long, a medium-sized dolphin, and it probably led a predominantly marine life rather than living in rivers like its modern South American relatives. The Paleobiology Database credits the name to Pyenson and colleagues in 2015 and lists the species in the family Iniidae.