Victoria's new state fossil emblem: Koolasuchus cleelandi

After 11,563 votes, the 125-million-year-old monster amphibian has been confirmed as Victoria’s fossil emblem.

A painting of a large amphibian poking its head out of water that is covered in petal
Koolasuchus cleelandi as it would have looked during the time of the dinosaurs.

Victoria, meet your official state fossil emblem—Koolasuchus cleelandi.

How much do you know about the animal chosen to represent this fine state of ours?

Not sure, or just need a refresher?

The museum’s senior curator of vertebrate palaeontology, Dr Thomas Rich, is here to help—and he should know, because he helped to name it.

‘It was a coincidence that I just couldn’t avoid,’ he says.

‘Typically these amphibians called temnospondyls have the suffix, suchus, which means crocodile in Ancient Greek.

‘The person who prepared the fossil was named Mrs Lesley Kool, and the fact that this animal once lived in a cold environment, putting together the name Koolasuchus was something I couldn't resist!’

So, it’s a pun on cool crocodile—who says science isn’t fun?

Professor Anne Warren described the animal in 1997, based on a fossilised lower jaw found on Boonwurrung country, near San Remo in south east Victoria.

The species name, cleelandi, is in reference to Michael Cleeland, the highly skilled fossil collector who found it.

But he was not the first to discover evidence of this long lost predator.

‘We had this first specimen that Professor Tim Flannery found in 1978 and we didn't know what it was for years and years,’ says Thomas.

That specimen was affectionately known as the ‘GOK’ (God only knows) for nearly 20 years.

‘It was only when more definitive material turned up that we were able to confidently call it a temnospondyl,’ says Thomas.

a curved fossil with teeth
The details preserved in this fossilised lower jaw allowed palaeontologists to determine it was the youngest temnospondyl.

Cold water croc

Koolasuchus cleelandi is an extinct primitive amphibian from the Cretaceous Period, 125 million years ago.

It would have been a fearsome predator in its day—up to three metres long, with a huge jaw bristling with fangs and tusks.

Imagine a newt or salamander crossed with a big saltwater crocodile and you have a rough idea of what it looked like.  

And the comparison to a crocodile is not too far off, because they both filled similar ecological niches.

Except crocodilians do not like the cold, and Koolasuchus lived at a time when Victoria’s average temperature was just above freezing.

‘Southern Australia was further south, and it was actually inside the Antarctic Circle,’ explains Thomas.

Australia and Antarctica were still joined as part of the supercontinent Gondwana, but only just.

A rift valley had formed between them, which was covered by a large flood plain and fast flowing rivers.

And lurking beneath the surface of the water would have been Koolasuchus, waiting for its next meal to swim by.

If you’re thinking, ‘Wait, how do we know anything about the speed of water flow more than 100 million years ago?’ it is all to do with the rock these fossils have been found in.

‘It’s a rather coarse sandstone for that area which makes us think this was a high-energy environment,’ says Thomas.

‘Which is interesting because when you look at the closest living amphibians, they are not temnospondyls but in Japan and China there are these giant salamanders, and they too live in very fast streams.’

The Cretaceous rift valley was an area highly populated by dinosaurs—everything from large carnivores to smaller wallaby-sized herbivores.  

‘It probably would have been fairly lush, but it was cold,’ says Thomas.

‘And this may be the reason they survived here when they were extinct everywhere else.’

In fact, when Koolasuchus was described it was unusually young for a temnospondyl.

All previous evidence suggested its relatives died out some 60 million years before.

To put that into perspective, ‘When we found it, it was equivalent to finding a living T-Rex today,’ says Thomas.

‘What’s happened since is that a few intermediates have been found, which you might say is almost expected, but it’s still by far the youngest one.

‘It seems like Victoria was the last hold out for this group, because it was polar.’

But as the climate changed, and the weather got warmer, the crocodiles moved in.

‘Here in Victoria there seems to be a replacement of the temnospondyls by the crocodilians and the only explanation we can came come up with is that the mean annual temperature rises about 5°C,’ says Thomas.

The evidence we now have for Koolasuchus is exclusively found in a stretch of coastline between San Remo and Kilcunda, in Victoria’s south east.

So, it is a uniquely Victorian animal—and a worthy choice for the state fossil emblem.

Keen to see Koolasuchus in the flesh? The original mandibles found by Michael Cleeland are on display in the 600 Million Years exhibition at Melbourne Museum.

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