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 years 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 that no on else had ever found and it adds to our knowledge base of organisms that once existed. But that is all it does.
Let’s return to our problem of how to find relatives of the first fish to walk on land. In our grouping scheme, these creatures are somewhere between the “Everythungs” and the “Everythings with limbs”. Map this to what we know of the rocks, and there is strong geological evidence that the period from 380 million to 365 million years ago is the critical time. The younger rocks in that range, those about 360 million years old, include diverse kinds of fossilized animals that we would recognize as amphibians or reptiles. My colleague Jenny Clark at Cambridge University and others have uncovered amphibians from rocks in Greenland that are about 365 million years old. With their necks, their ears, and their four legs, they do not look like fish. But in rocks that are about 385 million years old, we find whole fish that look like, well, fish. They have fins. conical heads, and scales; and they have no necks. Given this, it is probably no great surprise that we should focus on rocks about 375 million years old to find evidence of the transition between fish and land-living animals.- Neil Subin pages 9-10
Just as I have been saying- go figure. Got that- he was looking for evidence of THE transition- he was not looking for any ole transitional form. And there isn’t any reason why a transitional form would be around millions of years after the transition occurred.
But anyway, the point is had the new data been available to Shubin- the data that puts the transition back to before 390 million years ago- that whole set up would be meaningless and wrong. Meaning he would not have been looking where he did.