Ancient River Dolphin Relative Discovered In Peru Desert

Auch - Flickr. Inia geofrensis río Negro, via Wikimedia Commons. CC BY 2.0

While Peru’s Pisco-Ica desert may seem a a little thirsty these days, the recent discovery of a plethora of fossilized marine vertebrates suggests that it was once far from its current dusty state. Among previous discoveries were gigantic raptorial sperm whales and an unusual walrus-like dolphin. Now, researchers have unearthed the fossilized remains of three dolphins that represent not only a new species, but also a new genus. The findings have been published in the Journal of Vertebrate Paleontology.

Researchers discovered the specimens in the upper-Oligocene-lower Miocene Chilcatay Formation which lies in the Pisco-Ica desert, south Peru. This period stretches from around 28 million years ago (Ma) to approximately 16 Ma. Compared with later on in the Miocene and the Pliocene epoch, scientists have found very few toothed cetaceans (an order of mammals including whales, dolphins and porpoises) from this period, making the new discoveries particularly exciting.

Of the three specimens discovered, two had remarkably well-preserved skulls which assisted in the classification process. After analyzing the skeletons, the researchers placed the dolphins within the family Squalodelphinidae. Only four genera had been previously included in this family based on specimens found in France, Italy, Argentina and the US.

The now extinct squalodelphinids were small- to medium-sized dolphins easily recognized by their elongated rostrum (beak) and single-rooted teeth. The new species, Huaridelphis Raimondii, is the smallest member discovered so far of the Squalodelphinidae family, but it was also equipped with the most teeth.

Interestingly, the researchers believe that the new species is related to a family of river dolphins called Platanistidae. This family had several members but is now looking rather bare with only one surviving species—the endangered South Asian river dolphin. This species, which is actually split into two different subspecies, can be found in the Indus and Ganges rivers.

River dolphins are peculiar cetaceans. Unlike their marine counterparts, they’re found in dark, murky rivers and consequently have tiny eyes and poor vision. Another feature that sets them apart is their long, slender beak that is lined with pointed teeth.

According to John Gatesy, a University of California Riverside professor who was not involved in the work, the newly discovered species is probably not related to other present day river dolphins such as those found in the Amazon. The fact that they are separate lineages suggests that different river dolphins probably independently adapted to freshwater life over time, Gatesy told Live Science.

According to the study, this new species is just one of several other interesting cetacean discoveries that been made by the team over the last few years. Given the sheer number of marine mammal fossils present at the site, the researchers are confident that many other specimens await discovery. 

[Via Journal of Vertebrate Paleontology and Live Science]

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