Prehistoric whale fossil explains a major mystery of evolution – how whales became the largest creatures on Earth

'Alfred' the fossilised whale skull to be unveiled at Melbourne Museum today!

Erich Fitzgerald and Tim Zieglar with 3D model of Alfred's skull

A remarkable 25-million-year-old fossil has provided a team of palaeontologists at Museums Victoria and Monash University with long-sought evidence of how whales evolved from having teeth to hair-like baleen – triggering the rise of the biggest beasts on the planet.

Nick-named 'Alfred', the fossil skull is from an extinct group of whales called aetiocetids, which despite having teeth were an early branch of the baleen whale family tree. Alfred’s teeth show exceptionally rare evidence of feeding behaviour suggesting an entirely new evolutionary scenario – before losing teeth and evolving baleen, these whales used suction to catch prey.

Today’s baleen whales – such as the Blue and Humpback – don’t have teeth. Instead they have evolved a hair-like structure called baleen that allows them to filter huge amounts of tiny plankton, like krill, from seawater.

As Dr. Erich Fitzgerald, Curator of Vertebrate Palaeontology, Museums Victoria explains:

"Filter-feeding is the key to the baleen whales’ evolutionary success. 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."

The fortuitous discovery of ancient bones on the coast of Washington state, USA by keen fossil collectors James and Gail Goedert introduced the team to 'Alfred' and gave clues to this palaeontological puzzle. 'Alfred' held the vital never-before-seen evidence of feeding behaviour: tiny horizontal scratches on the inner surface of Alfred’s teeth.

This unusual type of tooth wear is only seen in a few living marine mammals (such as walrus) that use a back-and-forth movement of their tongue to suck in prey, and incidentally rough material like sand.

Dr. David Hocking, Postdoctoral Fellow, Museums Victoria and Monash University explains:

"These horizontal scratches on Alfred’s teeth suggest that he would have sucked small prey into his mouth, much like we would suck a milkshake up through a straw."

Dr. Felix Marx, Postdoctoral Fellow, Museums Victoria and Monash University says:

"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."

The team is now uncovering the rest of Alfred’s skeleton, as well as other fossils from Australia that provide exciting insights on how baleen whales began, hints Dr Erich Fitzgerald, “There are genuine surprises. We’ve only just begun to decipher the earliest and strangest pages of the baleen whale story.”

This paper is published in Museums Victoria’s peer-reviewed scientific journal Memoirs of Museums Victoria. You can access it here.

This research was supported by a Marie Sklodowska-Curie Global Postdoctoral fellowship to Felix Marx, an Australian Research Council Future Fellowship to Alistair Evans, an Australian Research Council Linkage Project to Alistair Evans and Erich Fitzgerald and an Australian Postgraduate Award to Travis Park. ‘Alfred’ was collected and generously donated to Museums Victoria by J. and G. Goedert, S. Benham and D. Reed.

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