Oryctodromeus (meaning “Digging Runner”) is a genus of small ornithopod dinosaur from the Late Cretaceous of Montana and Idaho, in the United States. The type species is O. cubicularis, named in 2007 by David Varricchio, Anthony Martin, and Yoshihiro Katsura. It was the first fossil evidence of a burrowing dinosaur discovered, with the type specimen being an adult and two juvenile inside a burrow. While it is the first published claim and first fossil evidence of a burrowing dinosaur, Robert T. Bakker said that Drinker from the Late Jurassic burrowed, but he never published this theory and there has been no fossil evidence. Since 2007, more dinosaurs have been thought to be burrowers, from Oryctodromeus’ contemporaries, Orodromeus and Zephyrosaurus, to the Australian Leaellynasaura and South Korean Koreanosaurus. It was a relatively small dinosaur, at 6.8 feet (2 meters).