(sigh… another creationist answer to my question.)
What would dolphins look like if they went back to land again? Would they become bipedal and have hands with opposable thumbs, or would they have hooves like their ancestors?
Dolphins were never land animals in the first place. Your question betrays a total lack of knowledge of biology, the fossil record and even the definition of evolution.
The idea of such as you believe is pure fantasy and only true in the wild imaginations of evolutionists.