Smithsonian paleontologists have discovered a previously unknown extinct species of dolphin, dubbed Arktocara yakataga, whose fossilized skull had been in the Smithsonian for over fifty years.
The research was published Tuesday in the journal open access PeerJ, and, as stated by one of the lead authors, Alexandra Boersma, museums’ collections are full of undiscovered treasures.
The mysterious skull
The damaged skull had been originally dug out from an ancient rock unit in southern Alaska, and given to the Smithsonian National Museum of Natural History back in 1951 by the geologist Don Miller.
From then on, it was never adequately studied until 2016, when Boersma and fellow Smithsonian paleontologist Nicholas Pyenson found it in the Museum archives and decided to investigate it.
The scientists created a digital model out of the skull, which was then carefully analyzed, concluding that it was 24 million to 29 million years old.
A dolphin’s tale
The age of the skull is of importance. Roughly 25 million years ago the Earth was in what is called the Oligocene: a cold, icy period, believed to be where cetaceans thrived and diversified.
However, while old and new whales are well known, this particular time and its inhabitants are not. All because not many rocks or fossils of this age are available for study.
This skull that likely had been picking up quite a bit of dust for over 50 years presented a rare opportunity to explore this peculiar period. Hopefully, the dolphin skull will also create interest in the preservation of the South Asian river dolphin, as only a few thousand remain, and these wonderful animals are the last remaining of this ancient dolphin lineage.
The modern cousin of the A. yakataga
The original location of the skull is fascinating, as the A. yakataga is an old relative of the Platanista gangetica, or South Asian river dolphin. This curious river dolphin, which is practically blind and swims on its side, has a long lineage of extinct ancestors.
“It was striking and kind of bizarre that this enormous group of marine dolphins that were up in the Arctic and all over the world has dwindled to this one species that’s stuck in freshwater systems in Asia,” notes Boersma.
The South Asian river dolphin, as its name indicates, is a tropical species that is geographically isolated, specifically in parts of Southern Asia, including India, Pakistan Bangladesh, and Nepal. The dolphins live in the freshwater river systems of the region, most commonly where there are plentiful prey and low flow.
The species had been considered a unity until 1998, where it was split into two subspecies, the Ganges river dolphin, and Indus river dolphin. Both of these subspecies are labeled as “endangered” by the International Union for Conservation of Nature and Natural Resources in their Red List of Threatened Species.
The causes for their unfortunate status are water pollution, the danger posed by fishing nets, being hunted for their oil and meat, the decrease of the water levels by irrigation, and perhaps most significantly, the creation of over 50 dams along the rivers, which segregate the dolphin populations, narrowing their gene pool.