Scientists have found out how the blue whales rose to become the biggest beasts the Earth has seen – and it's all down to their teeth.
The skull of a 25-million-year-old fossilised whale, nicknamed Alfred, has helped palaeontologists join the dots on how whales' teeth evolved into fine, hair-like bristles called baleen.
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Why are baleen whales so big?
A 25-million-year-old fossil called 'Alfred' reveals how whales evolved to be the biggest beasts on earth.
Belonging to an extinct group of whales called Aetiocetus, Alfred's fossilised remains contains the first evidence that this group used suction methods to catch their prey, in the same way blue whales and other baleen whales do today.
Monash University palaeontologist Felix Marx said horizontal scratches on the surface of his teeth revealed hard food or sand had repeatedly scraped past the teeth, leaving visible parallel channels.
He said the deep scratches provided a rare insight, as behavioural clues are almost never left behind on fossilised remains.
"We can now say for sure what these animals were doing and that's something incredibly special," Dr Marx said.
"This means we can finally figure out how the transition from teeth to baleen actually happened."
Today's baleen whales, including the blue whale and humpback whale, don't have teeth but use their baleen to filter-feed.
![Palaeontologist Dr Felix Mark with the 25-million year old skull of Alfred the whale.](/web/20161130162240im_/http://www.theage.com.au/content/dam/images/g/t/0/o/8/p/image.related.articleLeadwide.620x349.gt02np.png/1480491138114.jpg)
Museum Victoria palaeontologist Erich Fitzgerald said this was the secret to their evolutionary success, as it enabled them to consume vast amounts of plankton and krill – and evolve to be the biggest monsters of the deep.
Alfred's fossilised skull and bones were collected in Washington State, in the US, by James and Gail Goedert, who donated the remains to Museum Victoria.
![An artists' impression of 'Alfred' showing off his teeth.](/web/20161130162240im_/http://www.theage.com.au/content/dam/images/g/t/0/2/o/x/image.related.articleLeadwide.620x349.gt02np.png/1480491138114.jpg)
Dr Marx said it was unclear how significant the fossil was when it arrived in bits and encased in rock a year ago.
"To be honest this was a bit of an ugly duckling," he said.
![Alfred's skull has helped scientists work out how whale's teeth turned into baleen.](/web/20161130162240im_/http://www.theage.com.au/content/dam/images/g/t/0/o/8/q/image.related.articleLeadwide.620x349.gt02np.png/1480491138114.jpg)
"But then we saw the teeth and thought 'no, there's something here'."
The whale would have been of average size – about 3.5 metres long with a skull no more than 70 centimetres long.
![The blue whale is the biggest beast the world has ever seen.](/web/20161130162240im_/http://www.theage.com.au/content/dam/images/g/t/0/m/0/1/image.related.articleLeadwide.620x349.gt02np.png/1480491138114.jpg)
The marks on the teeth not only indicate that Alfred was a filter feeder but that he also fed from the sea floor.
The scratches would likely have been caused from sediment such as sand or bits of shell rushing past in the water which contained prey such as sea worms, fish and squid.
![A diagram showing how the whale fed using suction power.](http://web.archive.org./web/20161130162240im_/http://www.smh.com.au/content/dam/images/g/t/0/4/f/n/image.imgtype.articleLeadwide.620x349.png/1480478862980.png)
A diagram showing how the whale fed using suction power. Photo: Museum Victoria
"He would have sucked small prey into his mouth, much like we would suck a milkshake up through a straw," Monash University paleontologist David Hocking said.
The findings by researchers from Museum Victoria, Monash University, London's Natural History Museum, the Smithsonian Institution and the Royal Belgian Institute of Natural Sciences have been published in the peer-reviewed journal Memoirs of Museum Victoria.
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