Fossils of Rare River Dolphin Discovered in Panama: Possible Clue to Understand the Evolution of Dolphins

Fossils of a rare river dolphin species dating back to 6 million years were discovered off the Caribbean coast of Panama on 18 June 2011.

The discovery of the new species, now classified as Isthminia panamensis, was made by scientists from the Smithsonian’s Nationwide Museum of Pure Historical Past. The fossil was discovered in marine rocks and many of the features of the jaws and skull point out that this must have been a marine mammal, reported Nicholas D Pysenson, the lead author of this fossil study, in a press release.

Rare River Dolphin

At present there are only four known species of river dolphins and all are endangered. These 4 are found either in rivers or along the coast. Of the four known species, the Yangtze River dolphin is likely to have become extinct now, reported the Smithsonian. The new fossil throws light on the fact there were many river dolphin species extant in the earlier times. This discovery reveals that this was not the case a few million years ago and that many species of river dolphins could have existed all across the globe.

‘The study of these fossils could reveal critical information of not only the evolution of dolphins, but also that of the changing ecosystems and geographies of the past,’ said Aaron O’Dea, a staff scientist at the Smithsonian Tropical Research Institute of Panama.

The structure of the fossil features a long snout, paddle-like flippers and flexible necks reflecting the fact that these mammals were adapted for hunting in rivers and had made the transition from being ocean-dwellers to river-dwellers. Another puzzling thing is that although some features like small eyes and elongated snout match with those of the modern-day Amazon River dolphins, the mammal whose fossils were recovered were clearly ocean dwellers, opined the researchers.


Pysenson said that when they first uncovered the fossil, it appeared to be that of a shark-toothed dolphin, an already known species. This fossil is made up of half a skull, bones from the flipper and shoulder and a lower jaw with almost the entire set of teeth intact. The researchers believed that the full length of the specimen could have been over 9 feet.

While the original fossil is kept secure within the Smithsonian Nationwide Museum of Pure Historical Past, a 3-dimensional printout is available for viewing in Panama’s BioMuseo. The research team chose the biological name of the species in recognition of the Republic of Panama, its people and the various scientists who have benefitted from studying its organic and geological histories.

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