SOLOMONS, MD – September 2, 2021 – A new species of extinct dolphin was just named based on a fossilized partial skull (Figure 1). The fossil was found by a scuba diver on a riverbed in North Carolina, U.S.A. However, in prehistoric times, it lived in the ocean (Figure 2). Amongst living dolphins, it is most closely related to the Amazon River dolphin. The new dolphin is named in a recently published paper that appeared in the journal Fossil Record (an open-access paleontological journal of the Museum für Naturkunde Berlin).
Ron Ison is a very experienced scuba diver who dives to collect fossils. On one of his dives in the murky, fallen-tree entangled conditions of the Meherrin River in North Carolina, he found a partial skull of a dolphin that had never before been seen. This dolphin was new to science and he donated his find to the Calvert Marine Museum in Solomons, Maryland. The new dolphin (Isoninia borealis) was named in his honor. The genus name is a combination of Ison, the family name of Ron Ison, and Inia, the epithet of the Amazon River dolphin (Inia geoffrensis), also known as the boto or pink river dolphin. The species name “borealis” is Latin for “northern”, a reference to the only known specimen having been found in the Northern Hemisphere.
There are three closely related species of modern dolphins that exclusively inhabit river basins in South America: Inia geoffrensis found within the Orinoco and Amazon River basins, Inia boliviensis that inhabits the Beni–Mamoré River Basin, and possibly Inia araguaiaensis from the Araguaia–Tocantins River Basin. The ancestors of these modern-day river dolphins were oceanic dolphins. More recently, these marine species became extinct, survived only by those species that successfully invaded South American freshwater rivers. In paleontology, it is not uncommon for a new species to be named based on only a few bones or a partial skull. Here is another example.
What amazes Dr. Stephen Godfrey, Curator of Paleontology at the Calvert Marine Museum and lead author on this paper, is that of the millions of individuals of this species that ever lived, this is the only known specimen (Figure 1)! “It is a one-of-a-kind!” says Godfrey. Obviously, the fossilized remains of some extinct species are exceedingly rare! Although this skull is incomplete, enough of it was preserved to show that it is unlike any other known dolphin—living or extinct. Because of its uniqueness, it could be given a new scientific name. What this new dolphin demonstrates is that during the Miocene epoch (6-7 million years ago), some relatives of the Amazon River dolphins were oceanic and far-removed from South America.
This work was co-authored by Stephen J. Godfrey (U.S.A.), Carolina S. Gutstein (Chile), and Donald J. Morgan III (U.S.A.).