Survivors are extinct ...
Current thinking in creationism supports the idea that volcanism was severe in the years following the flood ... its probably that some of the species on the ark couldnt adapt to rapid climate changes ...
Huge dinosaurs certainly werent on the ark, they perished in the flood ... their survivors were chosen for extinction by natural selection ...
Yes, the survivors are extinct, which kind of begs the question why they were lined up two by two if none of them could survive until the beginning of recorded history. It wasn't that long.
Before landing at Ararat, did Noah drop off all the Marsupials in Australia, then swing by America to let off the bison and other critters that couldn't reasonably be expected to swim the Atlantic? That seems to be a glaring omission in the account.