Agh...I can't choose only one...but I do have a favourite of each type:
Small herbivore: Dracorex
I'm a potterhead, and its name Dracorex hogwartsia means "Dragon king of Hogwarts".
So is there anything cooler than naming them after Rowling's characters?
Small carnivore: Deinonychus
I love the crest, comb and tail ridge, they give it a unique look.
Medium herbivore: ...
Fine, I don't have a favourite hadrosaurid. Sorry.
Large carnivore: T-REX!
Well, I haven't unlocked every dinosaur, so Giganotosaurus may soon be crowned in this place.
Giant herbivore: Diplodocus
So remember the Science mission in Isla Tacaño, where you have to keep one stressed for 3 minutes? After the mission was completed, the first thing I did was give this Diplo a few herding companions. She deserved it.
Armored herbivore: Torosaurus
I don't know why, maybe because it's like a slimmer Triceratops