Juncitarsus gracillimus was named by Olson and Feduccia (1980). Its type specimen is USNM 244318, a limb element (left tarsometatarsus), and it is a 3D body fossil. Its type locality is low buttes, northeast of Twin Buttes, which is in an Eocene terrestrial siliciclastic/sandstone in the Bridger Formation of Wyoming. It is the type species of Juncitarsus.