That's truly amazing, in fact all the members of the "Creation Trio" from Gen IV games are based on different species of dinosaurs. You should do also a Giratina Origin Form, maybe with features ispired from plesiosaurus since it has a serpentine look.
This is an awesome rendition of Giratina. I always thought it would be some sort of dinosaur, too, since it is a part dragon type after all and it's looks remind me of one. Especially this forme. The Origin forme is more centipede-like, but I'd still make it more serpent than insect like.
Anyway, I think you did great job interpreting this legendary. You made it realistic and very believable yet you still manged to maintain its magnificence and legendary status. Good job on the details, too!