Evolution did not happen like this:

   fish ---------> amphibian --------> reptile

but like this:

    fish   amphibian   reptile
      \       \          /
       \       \        /
        \       \      /
         \       \    /
          \       \  /
           \       \/
            \      Amphibian/reptile common ancestor
             \    /
              \  /
               \/
               Fish/amphibian common ancestor
              /

See?  No one of the three groups is expected to be "more evolved than," or
"in between" the others.