Shark is moddable, though I do not know to what extent. IBC made a mod for it a while back, as I recall.
As for Hibbertopterus- the giant sea scorpion archetype is already covered with Jaekelopterus, so that would be kind of redundant.
EDIT: I'm moving this thread back to the old forum. Please continue discussion there.
http://z3.invisionfree.com/The_Carnivor ... topic=5120