Ancient whale sucked up prey vacuum cleaner-style

Natalie Muller -

An early ancestor of the blue whale hoovered up its prey rather than using baleen plates to filter feed.

The fossilised jaw of a 25-million-year-old baleen whale is shedding light on how the mouths of Earth's largest ever animals evolved.

The 30cm fossil, found in the coastal town of Torquay, Victoria, shows the earliest of these marine mammals had vastly different feeding habits to its modern descendants. Museum Victoria palaeontologist Dr Erich Fitzgerald says that the jaw of this early whale, Janjucetus hunderi, shows that ancient baleen whales didn't have the flexibility to gulp and filter enormous volumes of seawater and krill, as living baleen whales do.

Janjucetus was a relatively small species and was likely no longer than 3m in length, says Erich.

In a paper published today in the journal Biology Letters, he argues the Janjucetus' rigid lower jaw joints and wide mouth were better suited to sucking up individual prey in the fashion of a vacuum cleaner.

"These new fossils are really the clincher in showing that they could not filter feed," Erich says. "Many scientists have argued that filter-feeding is really one of the key distinguishing features of all baleen whales. Now it seems that is not the case, and that it evolved later."

He says 'suction-feeding' was most likely an evolutionary precursor to the filter-style of feeding that baleen species such as the humpback whale and blue whale are known for today. A huge mouth, loose lower jaw and baleen (a hair-like structure inside the mouth that serves as a sieve) are vital for species such as the blue whale to be able to strain sea water and consume as much as 3000kg of krill per day.

The first baleen whales had a wide upper jaw, but they didn't have baleen. Erich argues that while this huge mouth may have evolved millions of years ago, it wasn't necessarily part of the evolutionary trend towards adapting to filter-feeding. Rather, it allowed early baleen whales to hoover up prey such as squid, large fish, sharks or even penguins, into their mouths.

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