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The scientists were on the 22-meter research vessel Australis, working off the tip of southern Chile, according to NOAA.
"This is the most different looking killer whale I've ever seen," Pitman told The Associated Press.
Pitman told National Geographic these whales have a more rounded head, a very small white eye patch and a pointier and narrower dorsal fin. They are also shorter in length than other orcas.
The AP reported that scientists have obtained a blubber and skin tissue sample from one of the whales in order to determine if the Type D killer whale is a distinct species.
“We are very excited about the genetic analyses to come,” Pitman said. “Type D killer whales could be the largest undescribed animal left on the planet and a clear indication of how little we know about life in our oceans.”