If you look at the Event Menu, you can get an sneak peak at some of next week’s events.
Darwinopterus is the featured creature in Clash of Titans. Kaprosuchus and Geosaurus will be the unlockable creatures, at least for high-level players. So, there’s some thing you don’t have to worry about, now.
I picked the amphibian at the beginning of the month not knowing it was an unlock.