Artistic reconstruction of a pod of Arktocara yakataga, swimming offshore of Alaska during the Oligocene, about 25 million years ago, with early mountains of Southeast Alaska in the background. Linocut art (a rare dark blue version here) by lead and corresponding author Alexandra Boersma.
The South Asian river dolphin (Platanista gangetica), also known as the Ganges and Indus River dolphin, is one weird cetacean. It lives only in freshwater river systems of Pakistan, India, Nepal, and Bangladesh, it swims on its side, it is functionally blind, and possesses some of the most elaborate and heavily pneumatized facial crests of any whale. It is also among the most threatened species of living cetacean, numbering only a few thousand remaining individuals.
Paleontologists have long been aware of Platanista's rich fossil heritage -- while singular today, over a dozen fossil genera are more closely allied with it, than to any other cetacean lineage. Together, the living South Asian river dolphin and its fossil relatives form a broad group, called Platanistoidea, which was globally widespread and included fossil forms that lived from the Oligocene to the Pliocene. The Oligocene is especially an interesting time because we know comparatively much less about marine mammal history from this epoch than other time periods, something that can be attributed to very hard rocks that are hard to find, and that haven't really been studied in too much detail.
The skull of Arktocara yakataga rests on an 1875 ethnographic map of Alaska drawn by William Healey Dall, a broadly trained naturalist who worked for several US government agencies, including the Smithsonian, and honored with several species of living mammals, including Dall’s porpoise (Phocoenoides dalli). Near the skull of Arktocara is a cetacean tooth, likely belonging to a killer whale (Orcinus orca), collected by Aleš Hrdlička, a Smithsonian anthropologist who worked extensively in Alaska, and an Oligocene whale tooth collected by Donald Miller, a geologist who worked for the US Geological Survey, and collected the type specimen of Arktocara. Donald Orth’s dictionary of Alaskan place names, published by the USGS, bookends the image. Image by James Di Loreto, Smithsonian Institution.
Today, we announced a new genus and species of Oligocene platanistoid, named Arktocara yakataga, published in the open-access journal PeerJ. The new genus and species is based on a single skull collected from Alaska in 1951, which has been in the Smithsonian's collections since that time. With this publication, we argue that Arktocara is potentially among the oldest crown toothed whales known, and certainly among the oldest platanistoids yet reported, and the most northerly. The name Arktocara is derived from the Latin for “the face of the North,” while Yakataga is the indigenous Tlingit people’s name for the region where the fossil was found. We also have provided an open-access and fully downloadable 3D model, mounted on the Smithsonian X 3D website; we thank Chesapeake Testing for X-ray scanning and supporting for digital image processing, as well as Materialise for technical support with 3D model rendering.