A skull of an extinct species of dwarf dolphin that lived between 28 and 30 million years ago has been discovered by a diver in the Wando River, in Charleston, South Carolina (United States).
The species, named Inermorostrum xenops , had no teeth and was smaller than other similar species such as the bottlenose dolphin that exists today.
Dwarf dolphin
This finding is important because it represents the first clear evidence of echolocating marine mammals feeding by suction .
According to assistant professor of geology at the University of Charleston, Robert W. Boessenecker , the dwarf dolphin had a short snout and completely lacked teeth. Therefore, the name of the genus, Inermorostrum xenops , means "defenseless snout":
We studied the evolution of snout length in cetaceans and found that, during the Oligocene (25-35 million years) and early Miocene (20-25 million years ago), echolocation whales rapidly developed extremely short snouts. and extremely long snouts, representing an adaptive radiation in feeding behavior and specializations.