Because really, maybe I'm looking in the wrong places, but you really don't see many of those. Oh sure, there's lots of reptilian-themed characters, and Beast Boy turns into prehistorical animals every now and then (I always loved in the cartoon where he turned into a T-Rex for effect), but there really aren't that many specifically dinosaur-themed characters around.
(and I know it's wrong, but I like the panel of him tied to the post there. Know your audience Marvel)