Iguanodon hands look like their doing a crude gesture. That's it that's the joke.

Iguanodon

Have we talked about the Iguanodon? It’s one of my favourite dinosaurs. Not just because of it’s hands (which are gnarly) but because of the history and intregue surrounding it’s discovery, misrepresentation, and eventual restoration as new information came to light. Iguanodon isn’t just a thumb-spike; it’s a thumbs up to the scientific process.