A reconstruction of a suction feeding aetiocetid (Artwork by Carl Buell)
A 98 feet long and 200 tons, blue whales are by far the largest animals on Earth. To get that massive, blue whales need to eat millions of calories. A day. They feed exclusively through baleen filter feeding and can gulp down nearly 8,000 pounds of krill per day. Baleen, a substance used for feeding found only in whales, is made out of keratin– the same stuff as human hair and nails.
These ragged plates at the opening of the mouth allow whales to filter thousands of gallons of water to strain out literally tons of krill to eat. Baleen makes a relatively recent appearance in whale evolutionary history, and now it seems it may have appeared more recently than previously thought according to a new study by paleontologist Felix Marx of Museums Victoria and Monash University and an international team of colleagues in the journal Memoirs of Museum Victoria.
Although there are 15 living species of filter feeding baleen whales, earlier in their 50 million year evolutionary history, whales just had teeth for chomping. Baleen does not fossilize easily, so paleontologists have been left wondering when and how exactly whales made the transition from teeth to baleen. A new 25 million-year-old fossilized whale skull from Washington may hold the answer.
The yet-unnamed species of extinct whale nicknamed “Alfred” is a member of a group called aetiocetids. Aetiocetids lived during the Oligocene (33-23 million years ago) and are early whales that had teeth for eating prey larger than krill, the preferred diet of modern baleen whales. It has typically been thought aetiocetids may have had both baleen and teeth, but this is difficult to prove without the presence of fossilized baleen.
How the fossil whale fed (Infographic created by David Hocking)
The tooth wear patterns on the new fossil seem to tell a strange and unexpected story. Almost all of the tooth enamel on the back side of the tooth, the part that touches the tongue, has been scoured away. All of the teeth are worn in this very peculiar fashion. Marx and colleagues noted that it looks most like tooth wear seen in other marine mammals that feed by sucking water and food through their teeth rather than biting at it. Walruses are known to feed in this manner and often have similar looking horizontal striations on the enamel surfaces of their teeth.
“Alfred shows how ancient baleen whales made the evolutionary switch from biting prey with teeth to filtering using baleen. 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,” Marx says. The tooth wear patterns also indicate that this animal also had no baleen. If there had been baleen behind the teeth, it would have prevented these scratches from being made.
This new whale fossil changes the interpretation of the evolution of baleen feeding. It means baleen may have evolved much later than previously thought if this sort of suction feeding was an evolutionary transition on the way to filter feeding. If you want to see for yourself and get an up close look at his teeth, it’s your lucky day–Alfred the whale fossil is being unveiled today at the Melbourne Museum in Australia for the general public.