Leptictidium (meaning delicate weasel) was a genus of small prehistoric eutherian from Eocene period. this extinct species of mammal lived alongside the dinosaurs, but died out when the tropical forests opened up.
Leptictidium had long hind legs, and probably used only those two legs when moving fast. Whether it hopped on two legs or ran bipedally is still a matter of debate. It had a long, bare tail which acted as a counterbalance, and a long, mobile snout to help it find its prey.
The leptictids were found right across Eurasia. Leptictidium itself was a specialised hopper with the best preserved specimens found in the Messel shales of Germany.