Does anyone not know what tiktaalik is? Very interesting.
Although tiktaalik predicted many decades ago, it was not discovered until quite recently. Who is to say there are NOT millions of these transitional fossils lying undiscovered out there in the rocks.
BTW, every living thing is a transitional species. You and I are transitional between the past and the future. It is quite possible that in a million years from now, humans may not "look" the same as they do today.