WASHINGTON, March 22 (UPI) -- Beluga whales and narwhals live in cold Arctic and sub-arctic waters but had ancient ancestors who mysteriously preferred warm waters, U.S. researchers say.
Why and when modern-day relatives of an ancient toothed whale that lived in warm Pliocene oceans 3 million to 4 million years ago, evolved to live only in northern latitudes remains a mystery, the say.
Researchers at the Smithsonian Institution have identified that species as Bohaskia monodontioides from a nearly complete skull found in Virginia in 1969.
Since Bohaskaia monodontoides was found in the temperate climate of Virginia and a second extinct beluga-related toothed whale, Denebola branchycephala, is known from a fossil found in Baja California, the researchers said, the cold-climate adaptations of narwhals and beluga must have evolved only recently.
"The fact is that living belugas and narwhals are found only in the Arctic and subarctic, yet the early fossil record of the monodontids extends well into temperate and tropical regions," Nicholas Pyenson said. "For evidence of how and when the Arctic adaptations of belugas and narwhals arose we will have to look more recently in time."