Early Whale Was Dwarf Mud-Sucker, Fossils Hint

Carolyn Barry in Sydney
for National Geographic News
December 23, 2009

An ancient dwarf whale unearthed in southeastern Australia captured its prey by slurping up mouthfuls of mud, a new study says.

The fossil whale, thought to be between 25 and 28 million years old, hints that mud sucking might have been a precursor to the filter feeding used by today's baleen whales.

Many modern whale species use hair-like structures called baleen to filter tiny prey such as krill from seawater. Baleen species include the humpback, the minke, and the largest animal ever to have lived on Earth, the blue whale.

The newfound fossil whale, which measures just nine feet (three meters) long, shares the same distinct jaw and skull structures as today's baleens.

But the tiny whale also had teeth, said study author Erich Fitzgerald, a paleontologist at Museum Victoria in Melbourne, Australia.

The odd combination suggests that the dwarf whale might have been adept at feeding on larger, chewier prey from the seafloor, using its tongue and facial muscles to "vacuum" along the sandy bottom, the study authors say.

Whale a Weird "Experiment"

Dubbed Mammalodon colliver, the dwarf whale was discovered in 1932 near the seaside town of Torquay, southwest of Melbourne (see map). Until now the fossils had remained relatively unstudied.

In addition to the whale's unusual feeding style, the new research shows that the dwarf appears to have evolved from larger ancestors.

The animal's small size, Fitzgerald said, was likely the product of evolutionary adaptations that allowed the species to exploit an ecological niche unusual for whales: suction feeding from the seafloor.

A cousin of the mud-sucking whale, the flesh-eating Janjucetus hunderi, lived around the same time and was also found in Torquay.

The two toothed oddities add to evidence that "the earliest baleen whales underwent a diversification of really quite bizarre, quite weird experimental forms," Fitzgerald said.

Findings published online December 21 by the Zoological Journal of the Linnean Society.




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