Scientists from the Smithsonian Museum excavating off the coast of Panama have made a discovery that is shedding light on the evolutionary past of dolphins. They have unearthed an ancient dolphin fossil they are calling Isthminia panamensis, which is a member of a brand new species and genus of dolphin who lived around 6 million years ago.
According to The Washington Post, although excavated in an ancient sea Isthminia panamensis more closely resembles modern river dolphins than their more common, oceanic cousins. Found in rivers around the world, the four existing river dolphin species are all endangered, with the Chinese river dolphin believed to be extinct. The transition from ocean-dwelling dolphins into rivers has long been puzzling to scientists, and this discovery sheds new light.
Isthminia panamensis exhibits characteristics similar to river dolphins, with a long, thin snout, paddle-like flippers, and flexible neck. These features allowed them to leave the busy oceans and travel up rivers in search of prey. This is an interesting evolutionary transition because dolphins originally evolved from terrestrial mammals who moved to the sea in search of better prey. Researcher Nicholas Pyenson of the Smithsonian Museum of Natural History said, “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. Isthminia now gives us a clear boundary in geologic time for understanding when this lineage invaded Amazonia.”
The time period that Isthminia existed on Earth, 6 million years ago, is the same period during which the oceans began to rise. This could be a clue about how animals on our planet adapted to changing conditions, and could shed light on how modern animals could be impacted by our changing planet today.