Even if you postulate that Pangaea took only a few thousand years to split up, you can't possibly be saying that koalas (and penguins and Micrixalus and bison and Anami rabbit and snow leopards...) lived close enough to Noah's apartment to (A) get there in time to board the ship and (B) make their way back home after the Flood.
And what did the koalas live on during their journey back home (which was a slow journey, as you can see from all those cute videos of koalas), considering that the eucalyptus trees had all been wiped out by the flood?
Hey, wait a minute, what did the koalas live on during their journey (very slow, hand over hand along the branches of the eucalyptus) through all that territory where eucalyptus trees don't grow on the way to the Ark in the first place?
Savanna, steppe, prairie, or pampas: They're all grasslands, the globe's most agriculturally useful habitats.
Grasslands go by many names. In the U.S. Midwest, they're often called prairies. In South America, they're known as pampas. Central Eurasian grasslands are referred to as steppes, while African grasslands are savannas. What they all have in common are grasses, their naturally dominant vegetation. Grasslands are found where there is not enough regular rainfall to support the growth of a forest, but not so little that a desert forms. In fact, grasslands often lie between forests and deserts. (See grassland photos.)
Depending on how theyâ€™re defined, grasslands account for between 20 and 40 percent of the world's land area. They are generally open and fairly flat, and they exist on every continent except Antarctica, ...
Humans have introduced cattle and sheep to all these grasslands, and they thrive. The question is: why are the pre-human grassland herbivores different in the different grasslands around the world if they all came off the ark and spread to the grasslands available when they could live in any of the grasslands?
Likewise the predators of the grassland herbivores also are divided geographically as well: why are the pre-human grassland predators different in the different grasslands around the world if they all came off the ark and spread to the grasslands available when they could live off the herbivores in any of the grasslands?
Why are there no gazelles and cheetahs in Australia or the Americas?
Why are there no kangaroos in Africa or the Americas?
Why are there no wolves^(1) or cougars in Australia?
Why are there no Bisons and grey wolves^(2) in Argentina?
Why are there no llamas in North America when there are cougars in North and South America?
So many questions.
Why is the biogeographic diversity sorted the way it is around the world if all the animals in the world came off the ark and distributed themselves according to their habitat needs?
This is just the tip of the iceberg of predator prey relationships in similar habitats in different parts of the world.
Monkeys, snakes, pigs, bobcats, etc etc etc
Evolution and biogeography history explain it.
Can creationists explain it in as consistent and credible a manner?
^(1) -- the thylacine was relatively shy and nocturnal, with the general appearance of a medium-to-large-size dog, except for its stiff tail and abdominal pouch similar to a kangaroo, and dark transverse stripes that radiated from the top of its back, reminiscent of a tiger. The thylacine was a formidable apex predator, -- not found in the Americas or Africa.
^(2) -- the maned wolf (Chrysocyon brachyurus) is the largest canid of South America. Its markings resemble those of foxes, but it is neither a fox nor a wolf. It is the only species in the genus Chrysocyon (meaning "golden dog") -- not found in Australia, North America or Africa.
Koalas didn't have to go from here to there and back. Only Turkey to Aussie.
The koala is an in-species daughter kind microevolved from the teddybear kind on the Ark. It wasn't until they got to Hawaii that they started getting sluggish and lazy and those cute little faces. Barely made it to Brisbane before they could barely move anymore.
BTW, the eucalyptus thing is just a faint. They all go in to Macca's when the researchers aren't watching.
There's probably no point in trying to be serious on this thread but oh well. I doubt Pangaea took more than a few days to split up. It's also possible that the koalas weren't yet koalas, descending from whatever ancestor was on the ark some time after the landing, possibly but not probably a teddy bear.
There was plenty of time for animals to reach the ark, it took a hundred years to build it after all. And there's no reason to think the trek to the part of Pangaea that became Australia took a particularly long time. Both animals and plants would have had extra vigor which they carried over from the superhealthy Creation period, evidenced by the long lives reported for human beings. So plants should have reestablished rapidly and animals should have been able to endure long treks. It took a while for all that original vigor to fade away to our present pathetic condition.
And Hawaii wouldn't yet have existed since volcanism began as a result of the Flood.
So to you "seriously" means Pangaea took a few days to break up, koalas evolved from another species on the Ark and all those toads and panthers and penguins and Anami rabbits and Micrixalus and millions of other species had some magical vigor that let them get from Mount Ararat to their particular homes through a landscape ravaged by forty days of mountainous waves?
And most of those other animals probably also evolved -- meaning MICROevolved -- after the ark landing too. And I have no idea how long it was before conditions were congenial enough for the animals to spread out. If Noah had laid in enough supplies they could have hung out around the ark for some period while the land dried out and plants got established.
You have to make an effort not to just shoot off the first debunking thought that comes into your little head.