This is part of a larger paper on evidences for evolution. But this part is particularly interesting.
"29+ Evidences for Macroevolution"
"Prediction 2.2: Atavisms"
http://www.talkorigins.org/faqs/comdesc/section2.html#atavisms Scientists believe that human embryos go through a stage where they have tails, but that the tail disappears eventually. Creationists claim that human embryos never develop boney tails and that the embryos just "look like they have tails."
This is highly misleading, because 1) not all tails are necessarily boney, and 2) some humans are actually born with boney tails.
Anyway, this paper does an excellent job of laying out the facts, including whales that are born with legs. (I wonder, is a whale with legs still of the "same basic kind" as the other whales? Is a "human" with a tail of the "same basic kind" as the rest of us?)