I would hope you would give me more credit than that. I am NOT asking for a modern onset of trans-mutation. I am asking is there a known species that has been identified as in some stage of that process today?
You would need a time machine to know if some present-day species were going to eventually have some mutated offspring that would become yet another species. All species now existing have the potential to create mutant descendants, so the book is far from closed. But we can't turn to the back of the book to see what's going to happen.
IMO, the presence of hidden genes that only get expressed as birth defects, eg. the legs of an occasional whale, constitute very strong evidence in favor the claim that whales are descended from land animals.