It is a common misconception that crocodilians have not changed much since they first evolved.
While it is true that modern crocodilians are ecologically similar to their semi-aquatic ancestors from the Mesozoic,
some extinct crocodilians changed greatly since that time.
Among these was the Australian crocodilian Quinkana.
While Quinkana was similar to other crocodilians in most respects, there were some key differences.
Its legs were longer and held in a more erect stance than in other crocodilians.
This would have increased drag while swimming but would have made it much easier to traverse on land.
Its teeth were also recurved and serrated,
as opposed to the conical teeth typical of most other crocodilians and their semi-aquatic relativities.
Its tail was also rounder than in other crocodilians, which would have made it a less capable swimmer.
Due to these features, as well as fossils being found in terrestrial environments such as caves,
it is thought that Quinkana lived a primarily terrestrial existence.
However, fossils of Quinkana are found close to what were once aquatic environments.
Based on this, some paleontologists have argued that Quinkana was semi-aquatic like other crocodilians.
However, even if it did spend some time in the water, its morphologny makes it clear that it spent more time on land
than any living crocodilian, even the Cuban crocodile.
Since Quinkana’s semi-aquatic ancestors wererestricted to large bodies of water, even if it was fully terrestrial
it makes sense that it was still better adapted towards the areas around these environments than the more arid regions
During the Cenozoic, there were other large, carnivorous terrestrial crocodylomorphs.
One group, the sebecids were neither true crocodilians nor descended from semi-aquatic ancestors.
Another group were the planocraniids, nicknamed the “hoofed crocodiles” for their hoof-like claws.
Quinkana instead belonged to Mekosuchinae,
a diverse group of crocodilians that evolved in the Eocene and lived in Australia and some Pacific islands.
While some mekosuchines were semi-aquatic like modern crocodilians, many others shared Quinkana’s terrestrial lifestyle.
The namesake of the group, Mekosuchus, has even been suggested to have been arboreal.
But despite their differences, mekosuchines like Quinkana were true crocodilian,
descended from the last common ancestor of the crocodiles,
alligators,
caiman,
and gharials.
Indeed, mekosuchines were more closely related to crocodiles than alligators and gharials are.
Quinkana itself consisted of four different species, all of which are only known from Australia.
The oldest, Quinkana meboldi, evolved in the Late Oligocene.
It was followed by Quinkana timara in the Miocene.
The snouts of both of these species were narrower than the latter species.
Quinkana meboldi and Quinkana timara were also rather small, only two to three meters long.
The larger Quinkana babarra evolved during in the Early Pliocene. Its snout was both the shortest and widest snout in the genus.
The most recent species, Quinkana fortirostrum, lived during the last Ice Age
and briefly coexisted with early humans when they first arrived in Australia.
Quinkana fortirostrum was also the largest species of Quinkana, growing five to six meters long.
Along with the huge contemporary monitor lizard Megalania,
Quinkana fortirostrum would have been the closest humans ever came to seeing a dragon.
Over time, the ecological role of Quinkana likely changed as the genus did.
While the specifics of its behavior are unknown, the earlier species likely served as medium sized predators.
On the other hand, Quinkana fortirostrum would have likely hunted larger species.
Some of its likely prey, such as the red kangaroo and the southern cassowary, are still alive today.
But fellow extinct species were also on the menu, such as the giant kangaroo Procoptodon,
the sheep sized monotreme Zaglossus hacketti,
and perhaps adolescent Diprotodon.
While there were other large predators like in Australia at the time,
such as Thylacine,
Thylacoleo
and the surviving saltwater
and freshwater crocodiles
the only predator larger than Quinkana fortirostrum was Megalania.
Unfortunately, Quinkana’s reign didn’t last.
While the reason for the extinction of Quinkana and other Australian megafauna remains debated,
it is often attributed at least in part to the arrival of humans.
Overhunting was probably not the cause Quinkana’s extinction, at least directly.
Armed with only primitive weapons, humans were more like to end up Quinkana’s meal rather than the other way around.
Instead, humans may have contributed to its extinction by overhunting the local megafauna
or by altering the habitat through mass burnings.
It is also been suggested that humans were not the only, or even main, factor in Quinkana’s extinction.
Parts of Australia become more arid at the end of the last Ice Age.
As mentioned earlier, Quinkana ais only known from less arid environments.
Therefore, Quinkana may have lost much of its habitat even without human interference.
. A combination of habit loss from both climate change
and human induced burnings would have been a major blow to the species.
Regardless of the cause of Quinkana’s demise, by 40,000 years ago,
Quinkana, along with most of Australia’s megafauna, was no more.
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