April 5, 2013
Dwarf Baleen Whales Lived During The Ice Age
Lee Rannals for redOrbit.com - Your Universe Online
Researchers from New Zealand's University of Otago found that the fossil of a dwarf baleen whale from Northern California, or Herpetocetus, is thought to be the last survivor of the primitive baleen whale family, dating just 700,000 years old.
Otago Department of Geology PhD student Robert Boessenecker said the previously youngest-known fossil of this whale were from the pre-Ice Age Pliocene epoch, which is about three million years ago. Baleen whales of this type were more common about 10 to 15 million years ago.
"That this whale survived the great climatic and ecological upheavals of the Ice Age and almost into the modern era is very surprising as nearly all fossil marine mammals found after the end of the Pliocene appear identical to modern species," Boessenecker said. "Other baleen whales underwent extreme body size increases in response to the new environment, but this dwarf whale must have still had a niche to inhabit which has only recently disappeared."
He said the find indicates that the emergence of the modern marine mammals during the Ice Age may have happened more gradually than previously thought. The team's discovery supports a recent hypothesis about the modern pygmy right whale. This theory says the Southern Ocean whale is not a true right whale but actually a member of the cetothere family and one of the closest relatives of the dwarf baleen whale.
"If their hypothesis is correct, this latest discovery indicates that other close relatives of the pygmy right whale nearly survived to modern times within the Northern Hemisphere," said Boessenecker. "In this light, Herpetocetus can be viewed as a Northern Hemisphere equivalent of the pygmy right whale: both are small-bodied with peculiar anatomy, possibly closely related, with feeding habits that are seemingly divergent from other baleen whales."
Baleen whales lack teeth, and use baleen to strain small prey like krill and fish from seawater. Many whales are able to gulp enormous amounts of water during lunges, while others filter prey from mud on the seafloor. Scientists believe Herpetocetus could not open its mouth more than 35 degrees, unlike any modern baleen whale.
Scientists reported in The Journal of Experimental Biology in March that the baleen whale system works best by entangling food as water flows across it. The system contains continually growing plate-like structures with an internal fiber core and a smooth exterior. Scientists knew very little about the mechanisms behind how a baleen whale traps food, until this study.