Tiktaalik- why it is a failed prediction
Tiktaalik is still being used as a successful prediction of something. I know it was supposed to be a successful prediction of universal common descent because it is A) Allegedly a transitional form between fish and tetrapods and B) It was found in the "correct" strata because allegedly no evidence of tetrapods before 385 million yeqars ago- plenty of fish though and plenty of evidence for tetrapods around 365 million years ago- Tiktaalik was allegedly found in strata about 375 million years old- Shubin said that is the strata he looked in because of the 365-385 range already bracketed by existing data.
The thinking was tetrapods existed 365 mya and fish existed 385 mya, so the transition happened sometime in that 20 million years.
Sounds very reasonable. And when they looked they found Tiktaalik and all was good.
Then along comes another find that put the earliest tetrapods back to over 390 million years ago.
Now had this find preceded Tiktaalik then Shubin et al. would not have been looking for the transitional after the transition had occurred- that doesn't make any sense. And that is why it is a failed prediction- the transition occurred some 25 million years before, Shubin et al., were looking in the wrong strata.
That said Tiktaalik is still an interesting find, something tha no on else had ever found and it adds to our knowledge base of organisms that once existed. But that is all it does.