Arctostylopida is an extinct order of placental mammals. They're animals of uncertain affinities to other groups and it was believed that they may be related to ungulates. Originally they were considered to be Northern relatives of Southern American notoungulates, closer to Notostylopidae. Now it seems more likely they were descendants of Asian Gliriformes, akin to rabbits and rodents. Their tarsal morphology shows moderate similarity to the gliriform Pseudictops, and strong resemblance to the tarsally conservative gliroid Rhombomylus.