The very concept of specie is an old idea that is meaningless. The differences in species are nothing more than a very large amount of adaptation.adaptation is not evolution, evolution means you are not the same species, while adaptation can be as minor as a change in size, still the same, just look different.
evolution fails at the TK boundary, utterly.
after that event the only thing left were a few small, underground mammals and some sea life.
even over million of years you are not going to go from rodent to crocodile.
case in point; we share dna with bananas