Giant Ancient Dolphin Skull Found: ‘We Couldn’t Believe It’

Scientists are intrigued by the unusual find

Scientists have discovered the fossilized skull of a giant river dolphin, a species believed to have left the ocean and found refuge in the rivers of the Amazon in what is now Peru 16 million years ago. The extinct species could have measured up to 3.5 meters in length, making it the largest river dolphin ever found.

The discovery of this new species, Pebanista yacuruna, highlights looming risks for the world’s remaining river dolphins, all of which face similar extinction threats in the next 20 to 40 years, according to the lead author of the new study published in Science Advances today.

Aldo Benitez-Palomino said the ancient creature belongs to the Platanistoidea family of dolphins, which typically lived in the oceans between 24 and 16 million years ago.

The surviving river dolphins were “remnants of what were once very diverse groups of marine dolphins,” he said, which were thought to have left the oceans to find new food sources in freshwater rivers: “Rivers are the escape valve… for ancient fossil we found, and it is the same for all river dolphins living today.”

According to The Guardian, Benitez-Palomino discovered the fossil in Peru in 2018, when he was still a student. He is currently working on his doctorate at the University of Zurich’s department of paleontology and says the publication of the research paper was delayed due to the pandemic.

He first noticed part of the fossil, a fragment of a jaw, while walking with a colleague. “As soon as I recognized it, I saw the teeth sockets. I shouted, “It’s a dolphin.” We couldn’t believe it. “Then we realized that this creature was not related to the pink dolphin of the Amazon River,” says the scientist. “We found an animal, a giant, whose closest living relative is 10,000 km away in Southeast Asia.”

Marcelo R. Sanchez-Villagra, director of the department of paleontology at the University of Zurich, said the find was intriguing. “After two decades of work in South America, we have found several giant forms from this region, but this is the first dolphin of its kind,” he said.

The fossil, Benitez-Palomino said, was remarkable both for its size and for the fact that it had no relation to the river dolphins that now swim in the waters where it once lived.

A common problem facing river dolphins, including the fossil’s closest living relatives that swim in the Ganges and Indus rivers, is the imminent risk of extinction. Urban development, pollution and mining were key reasons, he said, and had already led to the extinction of Yangtze River dolphins.