A whale with large eyes, razor sharp teeth and a slimline body for hunting has been found on the southeast coast of Australia. But this whale died 26 million years ago (mya).
Fossils of the whale uncovered at beach town Jan Juc along Victoria’s surf coast – on Wadawurrung Country – have been identified as a new species dubbed Janjucetus dullardi. The whale is described for the first time in a paper published in the Zoological Journal of the Linnean Society.
The partial skull with ear bones and teeth were found in 2019 by Jan Juc local Ross Dullard who donated the fossils to Museums Victoria.
A baleen whale, but not like you know
Museums Victoria’s palaeontologists say the ancient marine mammal provides new insights into the early evolution of baleen whales – the group known as Mysticeti.
Modern baleen whales can be giant. Species like fin, blue and right whales are the largest animals ever, with some growing to more than 30m long and 100 tonnes. They are slow, graceful filter feeders.
The J. dullardi specimen was a relative tiddler at just a little more than 2m long – about the size of a modern common dolphin – and adults probably didn’t grow to much more than 3.5m. But this ancient relative of baleen whales, while small, packed a punch. It was a fast swimmer with forward-facing eyes and sharp teeth, probably hunting more like a shark than its modern filter-feeding relatives.
Janjucetus dullardi calf and mother. Artwork by Ruairidh Duncan.
Cosmos spoke with lead author Ruairidh Duncan and lead author Dr Erich Fitzgerald about the discovery.
“We know that the first baleen whales separated from toothed whales about 30-something million years ago, and they all have these common traits … that you still see in baleen whales today,” says Duncan who is a PhD student at the Museums Victoria Research Institute and Monash University.
Duncan says baleen whales have specific features, including a flattening and broadening of the jaws and unique infraorbital plates – the floor of the eye socket. These are features seen in J. dullardi.
“Initially, we didn’t think it had many of the features preserved that are diagnostic for baleen whales,” adds Fitzgerald who is the Senior Curator of Vertebrate Palaeontology, Museums Victoria Research Institute. “Then, as we went through the parts of the fossil skull that were preserved, we realised we had one part of the skull from the floor of the brain case. That bone has an anatomy which is unique to all baleen whales.”
This bone in toothed, echolocating whales and dolphins is a thin and narrow crest, Fitzgerald explains.
“But in baleen whales it’s not a thin crest, it’s an inflated, bulbous knob. That is only seen in Mysticises. There’s no doubt about what we’re looking at here.”
Specific species
The first whales evolved from land mammals which transitioned into Earth’s ancient seas more than 50 mya. J. dullardi belongs to a group of early whales called mammalodontids which only lived during the Oligocene epoch 30–23 mya.
J. dullardi is the third mammalodontid species found in Victoria and the fourth worldwide with the other found in New Zealand (Aotearoa).
Janjucetus dullardi family. Artwork by Ruairidh Duncan.
The new specimen is the first mammalodontid to preserve both teeth and inner ear structures in detail. These are key features for figuring out how early whales fed, moved and behaved.
J. dullardi is also the second species of ancient whale which has been assigned to the genus Janjucetus – named for the beach town where they were discovered. J. hunderi was named in 2006 by Fitzgerald, was roughly 3m long and also lived in the middle of the Oligocene.
The researchers explain that the teeth in J. dullardi’s upper cheek have a pronounced crest not seen in the teeth of J. hunderi.
“Even though it might seem a really minor difference, that sort of difference in anatomy, generally speaking, isn’t due to individual variation within a species. That’s a difference you see between 2 generally similar but clearly distinct species, hence the decision to name it as a new species within the previously named genus Janjucetus,” explains Fitzgerald.
While J. dullardi’s age is well constrained to roughly 26 or 27 million years, J. hunderi has a wider possible age range. “They may have existed at the same time, or they may be what we call a chronospecies where an animal evolves into another animal,” Duncan says.
This, Fitzgerald hastens to add, can only be tested with the discovery of more Janjucetus fossils.
Milking fossils for all they’re worth
The researchers also ruled out the difference in teeth being a sign of a specific developmental phase of a growing whale. They say the enamel of these early whales mineralises very early in their lives. They also note that fossil evidence suggests early toothed baleen whales had only one generation of teeth – that is, they do not have milk teeth which fall out to be replaced by adult teeth like in humans.
Ruairidh Duncan and Dr Erich Fitzgerald Erich with the partial fossil skull of Janjucetus dullardi. Photographer: Tom Breakwell. Source: Museums Victoria.
Duncan notes that “10 million years earlier, the early ancestors of these animals did have milk teeth”.
Fitzgerald says understanding that transition from having 2 generations of teeth could help explain baleen whale evolution, as well as why most dolphins have a large number of teeth which are all the roughly the same shape and size – something which is rare among mammals.
“That is one of the outstanding questions of whale evolutionary biology, and one which we don’t yet have the fossils … to address, because it requires finding a fossil of an early toothed baleen whale or early echolocating dolphin relative that is a juvenile on the cusp of losing milk teeth and the permanent adult teeth starting to come in,” Fitzgerald notes.
“A striking provincialism”
Oligocene seas around southern Australia were much warmer than today, despite the entire continent being much closer to the south pole than it is at present, due to warming which raised global temperatures toward the end of the period.
Some whale groups – like early large, toothless baleen whales called Eomysticetidae – were widespread during the Oligocene. Eomysticetid fossils have been found in Australia, New Zealand, Japan, and North America’s east and west coasts.
But Fitzgerald says there is “a striking provincialism” in the distribution of other whales during the Oligocene.
“Mammalodontids are only known from Australia, except for one named species, Mammalodon hakataramea, discovered in New Zealand,” Fitzgerald says. “Of all the hundreds of whale fossils known from New Zealand from the Oligocene epoch, there is one mammalodontid. In the Oligocene of Victoria, more than 80% of all the whale fossils found are mammalodontids. And they’re comparable sample sizes, so that’s a significant difference.”
“So, when it comes to some of these smaller body size species, based on the available fossil record, they seem to have much more restricted distributions.”
Uncovering an ancient ecosystem on a Victorian beach
Duncan lists a plethora of other Oligocene animals known from the Jan Juc Formation including a spear-toothed dolphin which had tusks sticking out of its jaws, fish species of which many would be familiar in the area today, cephalopods and an ancestor of the Port Jackson shark.
He also notes that older rocks might reveal the first ancestor of the mammalodontids which is believed to have lived about 30 mya.
The researchers leave us with tantalising hints of big announcements to come from the fossils of Jan Jac.
Jan Juc beach. Photographer: John Broomfield. Source: Museums Victoria.
“This is not the end. There are other species of mammalodontid which have already been found but have not yet been named and have not yet been fully analysed,” Fitzgerald says.
In addition to the 3 named mammalodontid species from the Late Oligocene of Victoria, he estimates that there are 3 to 6, and possibly more, that are awaiting formal description and naming.
“Some of those are fairly similar to Janjucetus and Mammalodon. Some of them are not.”
“What is clear in terms of the emerging picture is that mammalodontids really were the principal group of cetaceans in the shallow coastal seas of southern Australia in the Late Oligocene,” Fitzgerald says excitedly.
“There is not really anywhere else in the world, at that time where you get fossil whales, where there is such a dominance of the diversity of whales as we see amongst mammalodontids in Victoria. And that, in itself, is really interesting.
“The explanation of that is only going to be reached with the inevitable further study of fossils that have been found, and the further search for the origin of this diversity of mammalodontids, not only at Jan Jac and elsewhere along the Surf Coast, but potentially at other locations in southeastern Australia.”