Guiana dolphin use electroreception in close range to sense the electric signals given off by its prey. They still use sound to hunt and locate like all toothed cetaceans. But echolocation does not work well in close-range, the signals can easily get confused during feeding frenzies.
Since the majority of the Guiana dolphin feeding is done near the seafloor, where there is a lot of silt from the rivers of South America, it is likely the evolved this adaptation.
Researchers began to train the captive species of Guiana dolphin to rest its head where they could examine it. They began sending electric signals to the dolphin - when the signal was received the dolphin was trained to swim and return for a reward. Then scientists put a plastic shield over the rostrum to block the crypts and found that the dolphin could not sense the electric signal.
This proves that Guiana dolphin use the crypts in their rostrums as electroreceptors. The possibility of other marine mammals having this ability is likely, now that scientists know what to observe.