New ‘missing link’ species of dolphin reveals how the animal moved from seas to rivers

Rmissing link of dolphinesearchers at the Smithsonian have identified an extinct genus and species of river dolphin that navigated ancient Earth’s deltas some six million years ago.

Researchers say the new species highlights the early evolution of river dolphins, marking a transition between saltwater and freshwater living.

Today, there are only four living species of river dolphins, but the new skeletal remains suggest the ancestors of today’s river dolphins were many and widespread across the globe.

The new species and genus, classified as Isthminia panamensis, was discovered in Panama.

It 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.

In comparison with other river dolphins—both fossil and living—the shape and size of these parts suggests that the full specimen may have been more than 9 feet long.

And while the species’ morphology – broad, paddle-like flippers, flexible necks and long, narrow snouts – suggest an animal well suited to hunting the silty bends of a coastal river, they also reveal an animal only recently removed from its ocean-bound relatives.

‘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,’ Nicholas D. Pyenson, curator of fossil marine mammals at the Smithsonian’s National Museum of Natural History.

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