Upon closer inspection, I realized that the leaf was a really large moth. (Like butterfly large. Sorry there's nothing in my photos to give an idea of scale. This guy's wingspan was about 3" across!) A little bit scary actually, though I don't really fear moths, except for what they tend to do to my favorite sweaters when I'm not looking.
Blinded Sphinx Moth or Paonias Excaecata. (Correct me if I'm wrong, lepidopterists.)
Great camouflage for the woods. Ah, nature. You know what you are doing.