In 1980 geologist Juan Carlos Sciutto discovered a rich fossil site six kilometres north of the Ocho Hermanos ranch in Chubut province.

In 1986, Rubén Martínez, Olga Giménez, Jorge Rodríguez and Graciela Bochatey described the theropod fossils and coined the genus and species Xenotarsosaurus bonapartei for them.

The generic name is derived from Greek xenos, "strange", tarsos, "tarsus", and sauros, "lizard", a reference to the exceptional build of the ankle.

The bones consist of two cotypes: UNPSJB PV 184, a series of two anterior dorsal vertebrae, and PVL 612, a right hind limb including the 611 millimetres (24.1 in) long femur, the tibia, fibula and astragalocalcaneum of the ankle.

The exceptional complete fusion, without sutures, of the astragalus and calcaneum, forming an element that is again fused to the widened lower end of the tibia, occasioned the generic name.