It’s good to see you once in a while here on BioLogos. But I wonder if you are mis-interpreting the point of having a term like “Intermediate Form” or “Intermediate Fossil”. In an earlier time, when scientists were intoxicated by the idea of having the entire animal kingdom unveiled before them, there was a misplaced zeal in using terminology that over-stated the value of a newly discovered fossil.
Let’s look at your example of the Tiktaalik. You say “So the definition has to be loose enough that it can be argued the data fits, but it lacks the clarity and reproducibility we normally expect of science.” And you imply that the value of Tiktaalik fossils is now lessened.
Here is what the Wiki article says: "Tiktaalik provides insights on the features of the extinct closest relatives of the tetrapods. Unlike many previous, more fishlike transitional fossils [<< EEEK!], the “fins” of Tiktaalik have basic wrist bones and simple rays reminiscent of fingers. . . . the proximal series can be directly compared to the ulnare and intermedium of tetrapods. The fin was clearly weight bearing, being attached to a massive shoulder with expanded scapular and coracoid elements and attached to the body armor… The bones of the forefins show large muscle facets, suggesting that the fin was both muscular and had the ability to flex like a wrist joint. . . .
The more robust ribcage of Tiktaalik would have helped support the animal’s body any time it ventured outside a fully aquatic habitat. Tiktaalik also lacked a characteristic that most fishes have—bony plates in the gill area that restrict lateral head movement. This makes Tiktaalik the earliest known fish to have a neck, with the pectoral girdle separate from the skull. "
As you can see, regardless of other “Intermediate Fossils” that are even older than the Tiktaalik, the unique combination of features in the Tiktaalik still make it an important category of fossils to study!
@Marty, as you will recall, when I first started examining this issue of “Transitional” fossils, I too was surprised that many of these extinct animal populations considered Transitional were not necessarily common ancestors of other similar fossils, nor ancestors of others. So when the article linked above went to the effort of explaining that even the term “Transitional” has pitfalls, I had to enthusiastically agree.
But now it would seem you don’t even like the term “Intermediate”. If I am correctly detecting your tone, I think it goes too far. And it would be good for YECs to come to understand the limits of how the term Intermediate is used - - so they can stop banging their heads against the wall on the older issue of “Transitional”.
Re-read the lines of text from the Tiktaalik article. It systematically reviews the differences in the fossil not normally found in animals conventionally classified as fish. This is a reproducible truth. The important milestones represented in Tiktaalik fossils, once confirmed, are always going to be important - - because of how well we know what it takes to be a fish - - vs. what it takes to be a land-loving tetrapod.
You conclude:
“But I still find “intermediate forms”, like “transitional forms”, to be more philosophical than scientific.”
Does Tiktaalik’s unique trait of a fish with a neck invoke philosophy? I don’t think so. It invokes anatomical truths, that will not change. If anything, the insistence that the adjective “Transitional” implies too much is the philosophical assertion. And for it to be answered, one has to decide if the term should be used even if the writer goes well out of his way to point out that the fossil is not a direct descendant or common ancestor of extinct populations that produced other (similar) fossils.
Yes, sometimes what was called a Transitional fossil was, in fact, a fossil from a cousin population…maybe even a fairly distant cousin branch. But every example of diversity within the animal Kingdom is a valuable indicator of how new forms come and go - - bringing with them some traits from the past, and show-casing new traits never seen before. Sometimes to see how a living form had to compromise to include a new feature is instructive in and of itself.
Marty, I think we all must honestly apply due diligence to what exactly is meant when the term “Intermediate Forms” is used. We must be clear that in many cases, it is Intermediate because of what it is showing (and will always show) … not because we know whether it is a descendant or ancestor of similarly shaped fossils.
To ask for more than this, @Marty, doesn’t seem fair, or necessary.