Newly Discovered Ancient and Extinct River Dolphin May Shed Light on Modern Species

Scientists have uncovered a new, ancient and extinct species of river dolphin. By examining fossil fragments, researchers are shedding more light on the evolution of today's freshwater dolphin species.

The recently discovered fossil dates from 5.8 to 6.1 million years ago. It was found on the Caribbean coast near Panama, and consists of half a skull, lower jaw with an almost entire set of conical teeth, right shoulder blade and two small bones from the dolphin's flipper. The shapes of these parts, in particular, suggest that the dolphin was probably more than 9 feet in length.

Today, there are only four species of river dolphins. All of these dolphins live in freshwater or coastal ecosystems and all are endangered, including the Chinese river dolphin which may actually now be extinct. Each of the modern river dolphin species show a common solution of adapting away from marine to freshwater environments with a body plan that includes broad, paddle-like flippers and flexible necks and heads.

"We discovered this new fossil in marine rocks, and many of the features of its skull and jaws point to it having been a marine inhabitant, like modern oceanic dolphins," said Nicholas D. Pyenson, one of the researchers, in a news release. "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."

The new species is called Isthminia panamensis. It's actually the closest relative of the living Amazon river dolphin. This means that the fossil can shed light on the evolution of this species.

The findings are published in the journal PeerJ.

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