March 23, 2012
Ancient Whales Tell The Story Of Their Modern Relatives
Smithsonian scientists have recently described a new species of toothed whale that once lived in warm climates during the Pliocene era 3-4 million years ago. These whales may have possibly been a close relative to the modern day Beluga and Narwhal.
Those happy looking whales, the Beluga and Narwhal, live exclusively in colder climates like the Arctic and sub-arctic. The challenge now for the scientists is to uncover the mystery of why the whales moved farther north when once they were content to live in the southern hemisphere.
When a complete whale skull was found in a mine in Hampton, VA, scientists were shocked to find evidence of such a toothed whale so far south in a temperate climate. They named the new species Bohaskaia monodontides and moved its skull to the paleontology collections of the Smithsonian´s National Museum of Natural History. At the time, the scientists believed the new species to be loosely identified with the Beluga, but no close study had been done.
That is, until 2010 when Jorge Velez-Juarbe, Smithsonian predoctoral fellow from Howard University, and Nicholas Pyenson, research geologist of the Smithsonian´s National Museum of Natural History, began to look more closely at the skulls of modern day Beluga whales and the skulls found in Virginia. Their research showed that this new species was closely related to the Beluga and Narwhal and even shared similar skull structure. However, there was enough unique data to warrant its placement as a new species and genus.
“Fossils referred to as belugas have been known from fragmentary bits, but skulls are so revealing because they contain so many informative features,” Pyenson says. “We realized this skull was not something assignable to a beluga, and when we sat down, comparing the fossil side by side with the actual skulls of belugas and narwhals, we found it was a very different animal.”
Not only were skulls and fossils of the Bohaskaia monodontides found in warm Virginia, but the skulls and fossils from another ancient, toothed whale were found in sunny California.
Denebola branchycephala was found in Baja, California and also shares close ties with the Beluga and Narwhal. Both Velez-Juarbe and Pyenson agree the cold-weather preferences of the Beluga and Narwhal must have evolved slowly and rather 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,” Pyenson says. “For evidence of how and when the Arctic adaptations of belugas and narwhals arose we will have to look more recently in time.”
The first place Velez-Juarbe and Pyenson will look? According to Velez-Juarbe, the change may be “related to oceanographic changes during or after the Pliocene affecting the marine food chain,” Velez-Juarbe says, “then competition or dietary preferences drove monodontids further north.”
Image 2: This is an artist's conception of Bohaskaia monodontoides, foreground. Behind and above are a modern-day beluga whale and narwhal. Credit: Carl Buell