Yep, that whale was plenty weird. Half narwhal, half beluga.

Science News shares the genetic solution to a puzzle that’s had marine biologists (and Greenland whale hunters) puzzled since the 1980s. Namely, what the heck was that weird whale we caught?:

DNA analysis of the whale’s skull confirmed it to be the male offspring of a narwhal mother and a beluga father, researchers report June 20 in Scientific Reports.

The animal was one of three unusual whales caught during a subsistence hunt in 1986 or 1987 in western Greenland’s Disko Bay, and the only one with any known remains. The three whales were all uniformly gray, with pectoral fins shaped like belugas’ and tails shaped like narwhals’.

The Inuit hunter, who gave the skull to researchers, said that he’d never seen such odd whales before or since, says Eline Lorenzen, an evolutionary biologist and curator of the National Museum of Denmark at the University of Copenhagen where the skull is housed. Disko Bay is one of the few places where belugas and narwhals overlap during mating season.

Previous DNA analysis of the decades-old skull was “lousy,” Lorenzen says. So she and colleagues used techniques for analyzing ancient DNA to determine that the animal had a roughly 50-50 mix of beluga and narwhal DNA, making it a first-generation hybrid.

Beluga whales have 40 peglike teeth. Narwhal females have no teeth, while narwhal males have one, sometimes two, spiraled teeth that pierce through their lip forming the famous “tusk.” The male hybrid had forward-pointing grooved teeth, but not the long tusk tooth.

It’s not clear whether the tusk sometimes gets in the way of narwhal mating, but it’s a distinguishing characteristic that might warn a female beluga that a male narwhal is a different species. Female narwhals, on the other hand, have a similar size and shape to female belugas, and might be more easily mistaken for them, says [whale biologist Randall] Reeves, who is based in Hudson, Canada. “A female narwhal being impregnated by a male beluga is pretty believable.”

Still, the pairing is unusual, even shocking, to some researchers who have studied the species for years with hardly an inkling of such intermingling. The beluga and narwhal branches of the whale family tree split off about 5 million years ago — about the same time human and chimpanzee ancestors went their separate ways.