The people over at Boing Boing have a posted an article from diterlizzi.com about where Gary Gygax got his ideas for monsters for the Dungeons and Dragons. The author of the article Tony D states that Gary got the idea for the monsters from a bag of prehistoric animals bought at a variety store. The monsters do not look like any real dinosaurs. Tony gives an interesting history on the figures at the link below.
http://diterlizzi.com/home/owlbears-rust-monsters-and-bulettes-oh-my/
In the comments someone mentions that the Ogre was a plastic Indian. Take a look:
Some scupltor in Hong Kong had some bad Chow Mein one night!!