Rugosodon is an extinct genus of multituberculate (rodent-like) mammals from eastern China that lived 160 million years ago during the Jurassic period.

Rugosodon is represented by a nearly complete fossilized skeleton, including a skull, that bears a strong resemblance to a small rat or a chipmunk.

[3] This means that the ankle is remarkably flexible, allowing the foot to hyper-extend downward—like a ballerina standing on pointed toes—and to rotate through a wide range of motion.

The site of the discovery consists of lake sediments with embedded volcanic layers, which also contained fossils of feathered dinosaur Anchiornis and the pterosaur Darwinopterus.

[4][3][7] Prior to the discovery of Rugosodon, scientists knew that multituberculates living 66 million years ago had highly flexible ankles.