Fossils reveal origins of filter feeding in baleen whales

MELBOURNE, Nov. 30 (UPI) -- Baleen whales are named for the long hair-like strands that hang from their mouth and filter food from the ocean. But baleen whales didn't always filter their food; their earliest relatives were biters.

New research offers evidence of the evolutionary transition from biting to filtering.

"Alfred," a 25 million-year-old fossilized whale skull, suggests baleen whale relatives began sucking up food like a vacuum, rendering their teeth useless.

"Alfred shows how ancient baleen whales made the evolutionary switch from biting prey with teeth to filtering using baleen," Alistair Evans, a scientist and research fellow at Monash University, said in a news release. "They first became suction feeders. Feeding in this way resulted in reduced need for teeth, so over time their teeth were lost before baleen appeared."

Filter feeding enabled baleen whales to evolve two of the largest species on Earth, the blue and humpback whales.

"Filter-feeding is the key to the baleen whales' evolutionary success," said Erich Fitzgerald, senior curator of vertebrate palaeontology at Museums Victoria. "But what has really eluded scientists since Charles Darwin is exactly how whales made the complex evolutionary change from biting prey with teeth to filtering plankton using baleen."

Alfred's teeth reveal evidence of suction feeding similar to the technique employed by walruses and other modern marine mammals, whereby the back-and-forth movement of the tongue pulls in water-based prey.

Alfred belonged to a baleen whale lineage called aetiocetids, the first suction-feeding whales.

Researchers detailed their discovery in the journal Memoirs of Museum Victoria.