Scientists discover ancient giant dolphin in depths of Amazon

The remains of the creature are millions of years old and it is thought to be the largest of its kind ever found

Scientists have discovered the 16-million-year-old remains of the “largest river dolphin ever found” after unearthing a huge fossilised skull in the Amazon.

Named Pebanista yacuruna, researchers at the University of Zurich found the new species in the Peruvian Amazon region.

They state in a new scientific paper that the Pebanista would have been measured between 3 and 3.5 metres, making it the largest freshwater dolphin to have been found.

An international research team made the find as they travelled on the Napo River in 2018 and started to collect dozens of fossils, however, after almost three weeks of exploration, the team made their most striking discovery.

The large dolphin skull was discovered by Aldo Benites-Palomino, the lead author of the study into the dolphin published in Science Advances, who was an undergraduate at the time.

Mr Benites-Palomino first caught a glimpse of a fragment of a jaw while walking with a colleague.

The Pebanista yacuruna is thought to have been 3 to 3.5 meters long (Jamie Bran)

“As soon as I recognised it, I saw the teeth sockets. I screamed, ‘This is a dolphin.’ We could not believe it,” he told The Guardian.

Their research found something just as remarkable as its sheer size: it is more closely related to river dolphins found in South Asia than to dolphins in the region it was discovered in.

Key aspects of the giant ancient dolphin show their relation.

Both the ancient dolphin and the river dolphins in South Asia have highly developed facial crests; bony structures that are synonymous with echolocation, which is the ability to ‘see’ using high-frequency sounds or echoes.

Echolocation is relied on for hunting, a critical factor as river dolphins usually live in muddier waters, making their vision weaker, explained Gabriel Aguirre-Fernández, a UZH researcher who also took part in the study.

The Pebanista also had an elongated snout with a lot of teeth, suggesting that they fed on fish, something else they share with river dolphins today.

Palaeontologists believe that this dolphin species would have belonged to the Platanistoidea, a group of dolphins that lived in the world’s oceans 24 to 16 million years ago.

Researchers believe that their marine ancestors before them would have invaded the freshwater ecosystems of proto-Amazonia that would have been filled with prey, and eventually adapted to the environment.

“Sixteen million years ago, the Peruvian Amazonia looked very different from what it is today,” Mr Benites-Palomino said.

The specimen of the dolphin found by researchers (Aldo Benites-Palomino)

“Much of the Amazonian plain was covered by a large system of lakes and swamps called Pebas.”

This system would have stretched across what is now today Columbia, Ecuador, Bolivia, Peru and Brazil.

However, around 10 million years ago, the Pebas would have eventually given way to the modern Amazonia, and new habitats would have led to the disappearance of prey, driving the giant dolphin into extinction.

The newly discovered species was named Pebanista yacuruna, which gets its name from the mythical aquatic people believed to live underwater in the Amazon basin.

Marcelo R Sánchez-Villagra, director of the Department of Paleontology at UZH, said that during two decades of work in South America, they have found several giant forms, but this is the first dolphin of its kind.

“We were especially intrigued by its peculiar biogeographical deep-time history,” Mr Sánchez-Villagra said.

However, being a palaeontologist in the Amazon comes with its challenges.

As the Amazon rainforest’s water levels become high, they restrict the experts’ fieldwork, so they must complete their work within dry seasons.

Fossils are only accessible when the river levels are low enough, and if fossils are not collected in time, they can be swept away in the rainy season and can be lost forever.

The giant dolphin’s fossilised skull is now permanently on display in the Museum of Natural History in Lima, Peru.