What I mean is this: Are there types of fish that have a most recent common ancestor with other types of fish that is less recent (farther back in time) than transitional forms like Tiktaalik?
If so, does that mean that humans (and therefore all amphibians, reptiles, birds, and mammals) are more closely related to a particular type of fish (for example, the Coelocanth) than that fish is to some other type of fish?
I think this is true- because I think fish had already started to diversify into forms like sharks, rays, bony fish, etc. before they crawled onto the land. But if it’s true, then why do we commonly seem to treat fish as a big group akin to reptiles, amphibians, or mammals, when they’re really made up of multiple such groups? It seems like we should separate the big (vertebrate) animal groups like this: sharks/rays, bony fish, jawless fish, and lobe-finned fish/tetrapods (or something like that). It doesn’t seem like the accepted taxonomic breakdown reflects this (for example, this).