Cut & Folded Custom Paper Toy. The jaw moves via a tab that sticks out the back.
This papercraft skull is downloadable as a DIY pattern PDF HERE. Make & decorate your own! (and of course send me a picture). Just print onto or glue to card stock, then cut, fold, and tape or glue via the directions.
Inspired by the great papercraft patterns from Readymech, NiceBunny, and Speakerdog. Via Home of The Skulls.
UPDATE 10/25: I've removed an unnecessary "glue here" X from the back of the jaw and replaced the PDF on the server with the new version.