Scientists have unearthed the fossilized skull of a giant river dolphin, a species believed to have abandoned the ocean and sought safety in Peru's Amazonian rivers 16 million years ago.
The extinct species would have been up to 3.5 meters long, making it the largest river dolphin yet to be discovered.
First Dolphin Of Its Kind
Paleontologist Rodolfo Salas stated that the skull belonged to the largest dolphin known to have lived in South American waters, measuring 3 to 3.5 meters (9.8 to 11.4 ft).
It was named Pebanista Yacuruna after the Yacuruna, a Peruvian mythological creature who dwelt in deep water.
According to the University of Zurich, the new dolphin species belongs to the Platanistoidea, a group of dolphins that lived in the world's waters between 24 and 16 million years ago.
The dolphin's skull, with its long snout, massive teeth, and well-developed forehead area, indicates that it was perfectly adapted to freshwater habitats.
These dolphins, like their contemporary counterparts, were most likely thickset with long snouts and small, nearly entirely blind eyes, and they relied heavily on echolocation to navigate murky waters.
They also possessed highly developed facial crests, which are specialized bone structures connected with echolocation - the ability to "see" by releasing high-frequency noises and listening for their echoes, which they use extensively for hunting.
"For river dolphins, echolocation, or biosonar, is even more critical as the waters they inhabit are extremely muddy, which impedes their vision," said Gabriel Aguirre-Fernandez, a University of Zurich researcher who also participated in this study.
Scientists discovered the fossil on a National Geographic Society-sponsored expedition to the Napo River in 2018.
The Amazon and Orinoco river basins still include the Amazon river dolphin, often known as the pink river dolphin or boto.
Scientists claimed that surviving river dolphins were "the remnants of what were once greatly diverse marine dolphin groups" that had abandoned the oceans to search for new food sources in freshwater rivers.
Closest Living Relatives
The study also revealed that the river dolphins of South Asia, notably those of the Ganges and Indus rivers in India, are the closest living relatives of the ancient dolphin.
Peruvian dolphins are substantially larger than their Asian counterparts.
According to Salas, the ancestors of both dolphins previously resided in the sea.
"This allowed them to occupy large marine spaces near the coasts of India and South America," Salas said.
The discovery of Pebanista in proto-Amazonian strata demonstrates that platanistids entered freshwater habitats not only in South Asia but also in South America, before the contemporary Amazon River dolphin, during a critical point in Amazonian evolution.
This also emphasizes the looming risks to the world's surviving river dolphins, all of which face identical extinction threats in the next 20 to 40 years.
Experts stressed that the fossil was notable for its size as well as the fact that it bore no resemblance to the river dolphins that presently swim in the waters where it previously lived.
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