Oddity Ark #23 (203) Quinkana

Today we have the second issue concerning paleofauna, a subject that makes me glad that the Australian megafauna of the Holocene is a lot tamer then it used to be. And remember if you want to request an issue on an amazing animal, fabulous fungus, perplexing plant or awesome paleofauna, don’t hesitate to leave a request in the comments.

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Oddity Ark #23 (#203)

Kingdom: Animalia

Phylum: Chordata

Class: Reptilia

Order: Crocodilia

[Clade]*: Mekosuchinae

Genus: Quinkana

Species:fortirostrum

* Post Cretaceous crocodile species are difficult to classify due to the radiation of the group after the KT Extinction Event that occurred approximately 65 million year ago (mya).

Related Species: Four species of crocodile are within the genus Quinkana. It should be noted that in modern taxonomy that the Mekosuchides and more closely related to modern crocodiles then alligators and caimans are(1).

Range: Fossils of Quinkana have only currently been discovered within north-western parts of Queensland.

IUCN Status: Quinkana fortirostrum is extinct and existed in the Pliocene and Pleistocene periods between 5 million years and 40,500 years ago (ICUN).

Land Croc!

Quinkana is a relatively large crocodile, with an estimated body length of 3-6m and a body weight of 200kg in weight. Unlike extant crocodile species that moved in a sprawling stance, Quinkana walked in a semi-erect stance and was able to run and gallop. While there are debates that Quinkana may have been semi-aquatic rather than being truly terrestrial, it was unable to drown prey with the conical teeth that extant crocodiles possess, and instead possessed blade like teeth akin to those of other terrestrial crocodiles and theropod dinosaurs (2).

Quinkana makes up one of the three large reptile predators of Pliocene and Pleistocene Australia: the others being the extinct Megalania (Varanus priscus) and the extant saltwater crocodile (Crocodylus porosus). Studies of Quinkana’s pelvic and pectoral girdles suggests that the species was a cursorial hunter (3), harassing prey and pursuing them until they succumbed from either blood loss or exhaustion. Prey items that Quinkana may have included species such as the giant kangaroo Procoptodon, rat kangaroo Propleopus and the wombat Ramsayia. The other large reptile predators were potential competitors with Quinkana and there is evidence that the species fought among its own kind for resources and territory.

Quinkana was connected to water, even if not sub-aquatic, due to is fossil remains were found in close proximity to ancient billabongs and rivers. As glaciation began to increase, the habitats in Australia began to trend towards open grassland and scrub land, habitats that Quinkana struggled to effectively hunt in, and led to increasing competition with the larger Megalania that was more well adapted to this habitat. Quinkana may have been present when the first Aboriginal Australians arrived on the mainland, and if so, likely predated on them, and was competition for prey with humans before it went extinct.

Ecology 101: A Guide to Environmental Mechanics #22 – An Introduction to Crocodile Evolution

It is often stated that crocodiles haven’t changed through their evolutionary lifespan, but this isn’t quite true. While the basic semi-aquatic crocodile body plan has been constant since it evolved in the Jurassic Period (200-145 mya) many other crocodile body plans have evolved throughout prehistory. The first crocodilians appeared in the Triassic period, were akin to Hesperosuchus, a small terrestrial animal that existed as scavengers and predators that had limited bipedal movement, as well as the typical quadrupedal movement practiced by modern crocodiles. Like the closely related dinosaurs, crocodiles remained small generalists until the extinction of the phytosaurs and labyrinthodonts that existed in the niche that extant crocodiles fill.

In the early Jurassic period, the early terrestrial crocodiles began to radiate into groups including three covered in this article; the Eusuchia, Notosuchia and the Thalattosuchia. The Eusuchia slipped into the niche vacated by the phytosaurs and included modern crocodiles, alligators and gharials, as well as the extinct Mekosuchides. While the Eusuchia are largely familiar, a few odd species evolved such as Mourasuchus a crocodile that moved from feeding on large prey to potentially become a filter feeder (4). In addition to Quinkana, the Mekosuchides evolved into snail eating arboreal forms such as Mekosuchus, a species that lived in Vanuatu and New Caledonia as recently as 3000 years ago.

While the Eusuchia evolved into a semi-aquatic form, the Thalattosuchia moved into costal habitats, evolving into forms akin to modern gharials. As the group evolved, the Thalattosuchia evolved the ability to drink salt water, a trait that keeps modern crocodiles from becoming truly marine animals, as well as reduced osteoderm coverage and deeper tails and webbed feet to improved sub-surface movement. By the end of the Jurassic period, the Thalattosuchia had evolved into species such as Metriorhynchus, a marine crocodile with a shark like tail fluke and flippers, becoming truly marine species, likely giving birth to live young at sea (5). Despite their adaptations to marine environments, the marine crocodiles became extinct at the beginning of Cretaceous due to rising sea level, with the niche filled by an extinct monitor lizards that would eventually evolved into the mosasaurs. The Eusuchia did evolve a few truly marine species in the Eocene Period, but never truly evolve into species akin to the Thalattosuchia.

As the other two groups of crocodiles moved into aquatic niches, the Notosuchia remained as a terrestrial group. The Notosuchia radiated into a number of species; including burrowing omnivores, small scavengers, fast moving predators and grazing herbivores. The majority of the Notosuchians remained small, a group that lived in South America, the Sebecosuchia, evolved into larger species such as Baurusuchus a 4m long terrestrial crocodile that competed with the abelisauride Carnotaurus for prey. Unlike many large creatures, the Sebecosuchia, managed to survive the KT extinction event, evolving into Barinasuchus, the largest post Cretaceous land predator, reaching a body length of 7.5m and a body weight of 1.6 tons (6). The remains of Barinasuchus are so large, that when they were first discovered, it was assumed that they were the remains of theropod dinosaurs that had survived the KT extinction event.

So, while crocodiles now only inhabit semi-aquatic niches, there is potential for the group to radiate into new niches. The two most marine adapted species; the saltwater crocodile and the American crocodile (Crocodylus acutus) only require an adaptation to allow them to drink saltwater to begin to survive for longer periods in marine environments. And while mammals currently dominate the top predator niches in most habitats, terrestrial crocodiles have existed alongside large mammal predators, and could potentially re-evolve on island habitats in a manner akin to the large varanids such as the Komodo dragon (Varanus komodensis). Most notably the Cuban crocodile (Crocodylus rhombifer) are already somewhat terrestrial, with long legs and are known to occasionally hunt on land, hinting at a potential evolution path towards become terrestrial predators.

References

1. www.arkive.com

2. Willis, P.M.A.; Mackness, B. (1996). "Quinkana babarra, a new species of ziphodont mekosuchine crocodile from the early Pliocene Bluff Downs Local Fauna, Northern Australia, with a revision of the genus". Proceedings and Journal of the Linnean Society of New South Wales. 116: 143–151

3. Stein, Michael D.; Yates, Adam; Hand, Suzanne J.; Archer, Michael (2017). "Variation in the pelvic and pectoral girdles of Australian Oligo–Miocene mekosuchine crocodiles with implications for locomotion and habitus". PeerJ. 5: e3501.

4. Langston, W. (1966). "Mourasuchus Price, Nettosuchus Langston, and the family Nettosuchidae (Reptilia: Crocodilia)". Copeia. 1966 (4): 882–885.

5. Herrera, Y.; Fernandez, M.S.; Lamas, S.G.; Campos, L.; Talevi, M.; Gasparini, Z. (2017). "Morphology of the sacral region and reproductive strategies of Metriorhynchidae: a counter-inductive approach". Earth and Environmental Science Transactions of the Royal Society of Edinburgh. 106 (4): 247–255.

6. Molnar RE, de Vasconcellos FM (2016). "Cenozoic dinosaurs in South America – revisited". Memoirs of Museum Victoria. 74: 363–377

Picture Credits

1. maxresdefault.jpg (1280×720) (ytimg.com)

2. Quinkana_timara_skull.jpg (2991×1857) (wikimedia.org)

3. Megalania-quinkana.jpg (1280×514) (squarespace-cdn.com)

4. 220px-Hesperosuchus.jpg (220×227) (wikimedia.org)

5. File:Metriorhynchus superciliosum.jpg - Wikimedia Commons

6. not_so_fast__mammals___by_hodarinundu_deei44d-fullview.jpg (1280×664) (wixmp.com)

If you want to see more amazing animals and plants, please check out the Oddity Arkive or past issues. And if you want even more animals, please check out dearly departed Impurest Cheese’s Guide to Animals which can be found here, or on the blog of long-suffering ecology intern @ficopedia

@cbishop, @batkevin74, @mrmonster, @lemillion, @shoto_todoroki and @spareheadone.

Last revenge of the archosaurs...

Nice one.

I actually have a really weird fascination with alligators/crocodiles, so this was really interesting to learn about.

@mrmonster: They are an interesting group indeed. The fact they are closer to birds then non archosaur reptiles alone is amazing.

I love megafauna

I’m betting these different phenotypes are pleiotropic eco-phenotypes that sprung out of high stress times.

They can express the change in body type within only two generations in these cases

@spareheadone: Thanks for the comment, who doesn't love megafauna (when it's not trying to trample, maul, gore or eat you)?

Well, the initial radiation was after a mass extinction event, and the further radiation after the KT Impact was a high stress environment as well.

Have you heard about the gene plasticity in snail kites? That's a good example of how genes are morphable to adapt to a new food source. While it's not quite rapid evolution, it is a good example of rapid adaptable morphology within a living species across relatively short times which eventually leads to evolutionary progress.

@sundown89:

No I haven’t read the kite one.

Is it the genes that are plastic or is it the transcripts and proteins that are plastic?

@spareheadone: It’s the phenotype for beak size. A new species of apple snail (four times the size of the native snail) escaped and over a decade (approximately 1.5 generations) the trend for larger beak size has selected.

Essentially it’s more sleight of hand then evolution, since phenotype plasticity leads to pre-coded morphological features. Snail kites had the genes to select for bigger beaks when exposed to the right stimuli during the bird’s puberty .

That said if a Darwinian Fitness advantage results from having a larger beak and we have only large beak size in the kites with an inability to select for smaller beaks regardless of stimuli then it’s evidence of micro evolution in action.

Nice! Australian Megafauna represent! :)

@batkevin74: Yep, I went through four other terrestrial crocodiles before settling on this one. Glad you enjoyed it.

@sundown89: The Diprotodon was awesome too along with the marsupial lion aka thylacoleo, if you're ever looking for suggestions

@batkevin74: Noted, and slotted into the list somewhere in 2023.

@sundown89: Sorry man I been too busy battle rapping with some dudes here on C.V. and I take a whole day to write a verse so I'm only seeing this right now! xD! I have 3 interesting pictures of crocodiles here, actually took from them in nature, not in captivity. Possibly one of the most badass animals on earth along with hippos who also terrorize them sometimes....

@lemillion: That’s not a problem, we all are busy at times, and those photographs of Nile Crocodiles are amazing. And taking on the African Buffalo, an animal known for its vindictiveness and aggressiveness.

@sundown89: Exactly cape buffalo is very aggressive. There is a footage of a African guy getting his vehicle almost flipped over by a herd of buffaloes. A crocodile's method of killing is a form of drowning by which it brings a victim into the water and rolls it violently around on the floor of the body of water in which it hunts. It's called something like a "death roll", if memory serves... To do this with a buffalo it's insanity!

@lemillion: Yep that would be the death roll. It’s mostly used to rip flesh from bone as extant crocodilian teeth are unsuitable for this task as much as for killing. Obviously Quinkana didn’t need to do that, with studies of its jaws showing that the bones couldn’t handle the stress. Then again Quinkana had the right dentition to shear flesh off the bone so it’s not a great loss.

@sundown89: Sorry, man, I thought I'd read this one. So, this was an ancient reason not to visit Australia- got it. :) @batkevin74, this thing was from your neck of the woods! ;)

@cbishop: Along with the marsupial lions, giant python and Megalania (essentially a bulked up Komodo dragon) to name just a few.

I’d rather take Pliocene Australia than Pliocene South America though. The giant carnivorous armadillos, sebeccid crocodiles, terror birds and sparassadonts all pose a unique and brutal way to die.

@sundown89: Of all the dinos, I'm still partial to the Triceratops. :)

@cbishop: Hmm I do see to be building a number of paleofauna articles.

Sometimes, I'm just mentioning an animal, but I'd certainly take an OA on them! :^D

@cbishop: Ah okay.

@yejj: You would probably enjoy this…

Great

@yejj: Thanks