Archicebus is a genus of fossil primates that lived in the early Eocene forests (~55 million years ago) of what is now Jingzhou in the Hubei Province in central China, discovered in 2003. The only known species, A. achilles, was a small primate, estimated to weigh approximately 20–30 grams (0.71–1.06 oz), and is the only known member of the family Archicebidae. As of 2013, it is the oldest fossil haplorhine primate skeleton discovered, and is most closely related to tarsiers and the fossil omomyids, although A. achilles is suggested to have been diurnal whereas tarsiers are nocturnal. Resembling tarsiers and simians (monkeys, apes, and humans), it was a haplorhine primate, and it also may have resembled the last common ancestor of all haplorhines as well as the last common ancestor of all