This is not a bad place to start looking for/at transitional fossils.

http://en.wikipedia.org/wiki/List_of_transitional_fossils#Cephalopods

Of course, if the Earth is only 6,000 years old, and humans have been keeping written records for most of that time, there could be contemporaneous accounts capable of rubbishing all this Wiki stuff.

It occurs to me, on reading my last sentence, that there could be readers (gentle/gentile or otherwise) who might suspect that I am being flippant. Such is not the case.

There never was nothing.