[neutrality]

Some embryos of the baleen whales begin to develop teeth. As with body hair, the teeth disappear before birth. Since there is no use for teeth in the womb, only inheritance from a common ancestor makes any sense; there is no reason for the intelligent designer or special creator to provide embryonic whales with teeth

http://www.talkorigins.org/features/whales/

[shubi]

Q: Mollusks, brachiopods and vertebrates have the
best fossil record because they have nice hard parts.
Some other groups (arthropods, sponges, etc.) also
have hard parts, but they are not as hard, nor are
they as easy to identify in pieces, so the record for
those can be expected to be less complete.

A: Typical scientist hedging. They know how weak their proof is compared to the literal King James Version
which says that God created each kind individually.

[judywillow]

Some embryos of the baleen whales begin to develop teeth. As with body hair, the teeth disappear before birth.

I'll agree that indicates a common ancestor; the question is as to method. To me the whole thing looks like an engineering change back in prehistory.