Fossils of unknown ancient dolphin species discovered in Panama

Scientists with the Smithsonian's National Museum of Natural History have revealed their discovery of a previously unknown species of ancient river dolphin. The fossils, first found in 2011 on the Caribbean coast of Panama, are believed to be between 5.8 million and 6.1 million years old, and include half of the animal's skull, a lower jaw with almost a full set of teeth, a shoulder-blade, and bones from a flipper. While there were clear signs the animal was a species of river dolphin, the fact that it lived in the ocean could lead to a better understanding of its evolutionary history.

The species has been named Isthminia panamensis and is believed to have been over 9 feet long. The area where its fossils were found had also been the site of other marine animal remains, indicating it was a saltwater species. This is combined with the fact that features of the skull and jaws are in line with the ocean-dwelling dolphins of today.

Despite all this, the researchers say Isthminia's closest living relative is the freshwater Amazon river dolphin. Their study, published this week in the scientific journal PeerJ, suggests that the new species may have been one of the first to begin its migration from marine to freshwater habitats. They note that all of the existing species of river dolphins had eventually moved from saltwater to freshwater.

"Many other iconic freshwater species in the Amazon — such as manatees, turtles and stingrays — have marine ancestors, but until now, the fossil record of river dolphins in this basin has not revealed much about their marine ancestry," said the Smithsonian's Nicholas Pyenson, lead author of the study. The hope is that the fossils will reveal not only more about the evolution of the dolphin species, but also how changing geographies and ecosystems played a part.

SOURCE Smithsonian