Paleontologists have discovered some fossilized remains in Panama suggesting that they originate from a long extinct species of river dolphin that is apparently previously unknown.
Scientists have named the ancient creature as Isthminia panamensis however, they consider this species as an enigma because even if they possess similar physical attributes of modern day Amazon river dolphins such as an elongated snout and small eyes, this distant ancestor apparently lived in the ocean.
Now, scientists say that this new discovery can also reveal clues about the ancient geology of the Amazon region. According to paleobiologist Nick Pyenson from the Smithsonian Institution located in Washington, D.C., the team believes that this dolphin thrived in a channel that used to connect to the Atlantic and Pacific oceans even before the formation of the Panama isthmus.
At first, Pyenson thought that the fossil from the rocky shoreline belonged to a shark toothed dolphin which is an already known ancient marine mammal. However, when the team returned and examined the specimens under laboratory conditions, they saw finer details that were never seen before and confirmed it was a new species of dolphin that can provide new insights about the evolution of freshwater dolphins today.
To date, there are only four species of river dolphins existing in freshwater or coastal regions where one of them, called the Chinese river dolphin, is thought to be already extinct as none of them were spotted recently.
The Panama fossil reveals that this ancient river dolphin is around nine feet long which is shorter than the modern Amazon river dolphin. According to co-author of the study, Aaron O'Dea from the Smithsonian Tropical Research Institute in Panama, the Isthminia is probably the closest relative of the Amazon River dolphin.
In ancient times, whales and dolphins evolved from terrestrial ancestors into full marine mammals but this river dolphin represents a reverse evolution by returning inland to freshwater ecosystems from the ocean.
Pyenson also adds that there are also many freshwater species found in the Amazon River such as turtles, manatees and stingrays that have descended from marine ancestors however, only little information has been known about the origins of the river dolphins.
The fossil of the Isthminia panamensis has also been dated back to 5.8 to 6.1 million years ago that reveals a link to a geologic timeline when this lineage has invaded the Amazon region. This new discovery is published in the journal, PeerJ.