An odd-looking whale skull in the Natural History Museum of Denmark was a mystery for nearly 30 years, but now a team of researchers has the answers. Apparently, the reason why the skull looks so strange is because it came from a narwhal-beluga hybrid.

Mysterious Whale Skull

In the 1980s, a hunter caught three odd-looking whales in Disko Bay in Greenland. The whales’ flippers looked like belugas’ and their tails looked very much like narwhals’, but their teeth looked very different from both narwhals’ or belugas’. What’s more, the creatures’ skins were consistently gray, when belugas have white skin and narwhals have brown speckles.

Of the three he caught, he kept one of the skulls and later on let researchers take it to the Natural History Museum of Denmark. Scientists immediately noticed the odd appearance of the skull, which is larger than the skulls of belugas or narwhals, and hypothesized that it might be a narwhal-beluga hybrid but could not confirm it.

Now DNA testing and isotope analysis reveals why the creatures looked so unique.

Narwhal-Beluga Hybrid

Upon testing the creature’s mitrochondrial DNA, researchers discovered that the creature’s mother was a narwhal and its father was a beluga, indeed making it a narwhal-beluga hybrid. Specifically, it is 54 percent beluga and 46 percent narwhal.

According to the researchers, there is no evidence of interbreeding between the two species in at least the last 1.25 million years, so this hybridization appears to be a very new or very rare occurrence. This means that the skull is the first and so far only evidence of hybridization between the two toothed Arctic whale species.