Amazon River Dolphin

The recently discovered species of ancient dolphin resembles the modern Amazon River dolphin, shown here.

Back in 2011, Smithsonian paleobiologist Nick Pyenson removed a fossil on the coast of Panama that had been embedded in the rocky shore.  As they raced against the incoming tide to dig a trench around the fossil, Pyenson and his team guessed that they were uncovering an ancient marine mammal known as the shark-toothed dolphin.  However, they were wrong.  Once he brought the fossil back to DC, Pyenson realized that it was like nothing that he had ever seen before.  Yet he soon realized that it was like nothing that anybody else had seen for millions of years.

According to a study published today in the scientific journal PeerJ, the newly-discovered fossil represents a new genus and species, the “Isthminia panamensis”.  This marine mammal poses a bit of a mystery, with an elongated snout and small eyes that resemble the modern-day Amazon river dolphin.  However, this aquatic creature didn’t live in the rivers of the Amazon, but rather in the open ocean.  Pyenson says he and the research team believe the animal lived in the channel that connected the Atlantic and Pacific oceans before the isthmus of Panama was formed.

This finding suggests that ancient dolphins living off the coast of South American made their way inland as ocean levels rose around 6 million years ago.  If the world enters another period of rising oceans, this line of research may help scientists predict what will happen next.  Pyenson hopes that reviewing deep evolutionary evidence about river dolphins will allow scientists to guess what their future will be.

The future of modern-day river dolphins is currently unknown.  Recently, one species of river dolphin, the baiji, was declared functionally extinct.  The animal, found only in the Yangtze River in China, the baiji’s numbers declined rapidly in recent years as the Yangtze river was overused for fishing, transportation and hydroelectricity.  There were efforts made to conserve the species, yet after an expedition in 2006 failed to find any baiji in the river, they were declared functionally extinct, the first known aquatic mammal species to become extinct since the Caribbean monk seal in the 1950s.  While a Chinese man videotaped what could have been a baiji swimming in the Yangtze in late 2007, the presence of just one or a few animals isn’t enough to save a functionally extinct species from true extinction.