Re: Gray treefrog tadpole tail problems
I've raised thousands of eggs through metamorphosis in research contexts and see kinked tails fairly regularly. I most commonly see this associated with water quality problems, especially salinity and acidity (hot water with a bunch of respiring tadpoles can turn water acidic pretty quickly). It would be hard to know what the water was like in the kiddy pool you pulled your tads from, but that would be my first thought.
As you found with your little friend, tail morphology in itself has almost no correlation with eventual skeletal morphology. That's because there is no skeletal structure associated with the larval tail. The straight structure of the tail is a result of the notochord development and lateral muscles which develops long before the skeleton ossifies. Of all the curvy tadpoles I've seen in my lab, pretty much all of them metamorph with no persistent problems.