Evolution: Help Needed

Well, I did say that I might try something completely different. Sorry about the low reward but I'm saving for a holiday. I'm sure you'll be able to make some extra cash should you manage to find the missing link. Good luck to one and all.

P.S. I'm much happier with this image than the last two. I still can't decide whether or not I like them (Dashing Flyby and Neon Curves).