Tiny, toothed mammalodontids were among the strangest of all whales. If alive today, they would be as iconically Australian as kangaroos. In a new paper published this week in the Zoological Journal of the Linnean Society, paleontologists described a new mammalodontid species — named Janjucetus dullardi — from a 25-million-year-old specimen found in Victoria, Australia.
Janjucetus dullardi calf and mother swimming through the shallow seas off Victoria, 25 million years ago. Image credit: Ruairidh Duncan.
“Today, some of the most iconic whale species, such as blue and humpback whales, are baleen whales,” said Monash University paleontologist Ruairidh Duncan and colleagues.
“These ocean giants use hair-like structures in their mouths, called baleen, to filter plankton — their main food source.”
“By contrast, mammalodontids were small-bodied (no longer than 3 m), big-eyed, and had short jaws lined with teeth.”
“Despite this description, we know that mammalodontids were, in fact, baleen whales … that lacked baleen.”
“They were like an offshoot from the main evolutionary branch leading to today’s toothless giants.”
All known mammalodontid species lived during the Late Oligocene epoch, between 27 and 23 million years ago.
And three out of four named species have been found on Victoria’s Surf Coast, south-east of Melbourne.
“The first mammalodontid was found in 1932, and in 1939 was given the name Mammalodon colliveri,” the paleontologists said.
“It had blunt jaw bones with extensive blood and nerve supply for face and lip muscles”
“Curiously, the teeth were worn down to the gums, suggesting it fed by slurping prey (along with abrasive grit) from the seabed.”
“In 2006, local naturalist Staumn Hunder found the first fossil of a species later named after him, Janjucetus hunderi.”
“This whale sported a robust triangular snout with sharp teeth and powerful jaw-closing muscles.”
“Although Mammalodon colliveri and Janjucetus hunderi hint at a surprisingly wide range of lifestyles for mammalodontids, the details of exactly how and when they became so different from other whales remain murky.”
The 25-million-year-old fossilized remains of Janjucetus dullardi were found on the coast at Jan Juc in Victoria in 2019 by school principal Ross Dullard.
“Janjucetus dullardi was about 2 m long — small enough to fit on a standard single bed,” the researchers said.
“This makes it the smallest fossil whale discovered in Australia, and perhaps the first fossil of a juvenile whale found here.”
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Ruairidh J. Duncan et al. 2025. An immature toothed mysticete from the Oligocene of Australia and insights into mammalodontid (Cetacea: Mysticeti) morphology, systematics, and ontogeny. Zoological Journal of the Linnean Society 204 (4): zlaf090; doi: 10.1093/zoolinnean/zlaf090
