They are created kinds; the question is how they were created.
I do not see any a priori theological reason to expect either special
creation of "kinds" or descent with modification (biological evolution) as
the method of creation, except for the strong tendency for God not to use
miraculous methods unless necessary. Platonic ideologies would advocate
special creation of kinds, but that is not authoritative.
There are two lines of evidence for descent with modification rather than
separate creation for the fish to amphibian transition. The first is the
presence of the fossil transitional forms. God could have created each one
separately and individually, in the sequence that they would occur had they
evolved, but why bother? If the ultimate goal was to specially create
amphibians, why not do so all at once? He did not need to practice or
experiment.
The second is the biochemical evidence. Comparison of amphibian DNA and
protein sequences with fish data on the one hand and amniote data on the
other will generally put the amphibians in the middle. Some sequences have
specific physical effects and may thus be affected by convergent evolution,
and the problems of long-branch attractors or other spurious effects of the
analyses must be addressed, but if you choose a sequence and method that
should, a priori, yield good results, a phylogeny should result showing
amphibians as derived from fish.
A caveat here is that many molecular biologists seem to assume that their
data and analysis are the final word, if not the first important word as
well. This is very much an area of ongoing work, and molecular biologists
are particularly notorious for not knowing much about the rest of biology.
David Campbell