Later authors proposed additional synapomorphies. An extensive study of "Herrerasaurus" by Sereno in 1992 suggested that of these proposed synapomorphies, only one cranial and seven postcranial features were actually derived from a common ancestor, and that the others were attributable to convergent evolution. Sereno's analysis of "Herrerasaurus" also led him to propose several new dinosaurian synapomorphies. "Herrerasaurus" was originally considered to be a genus within Carnosauria, which then included forms similar to "Megalosaurus" and "Antrodemus" (the latter is equivalent to "Allosaurus"), even though "Herrerasaurus" lived many millions of years before them and retained multiple primitive features. This carnosaurian classification was amended upon by Rozhdestvensky and Tatarinov in 1964, who classified "Herrerasaurus" within the family Gryponichidae inside Carnosauria. The same year, Walker published a differing opinion that "Herrerasaurus" instead was allied with Plateosauridae, although it differed in possessing a pubic boot. Walker also proposed that "Herrerasaurus" may instead be close to "Poposaurus" (now considered a pseudosuchian) and the unnamed theropod from the Dockum Group of Texas (now assigned to the rauisuchian "Postosuchus"). In 1985, Charig noted that "Herrerasaurus" was of uncertain classification, showing similarities to both "prosauropods" and "carnosaurians". Romer (1966), simply noted that "Herrerasaurus" was a prosauropod possibly within Plateosauridae. In the description of "Staurikosaurus", Colbert noted that there were many similarities between his taxon and "Herrerasaurus", but classified them in separate families, with "Herrerasaurus" in Teratosauridae. In 1970, Bonaparte also proposed similarities between "Herrerasaurus" and "Staurikosaurus", and while classifying them both clearly as in Saurischia, he stated that they appeared as though they could not be placed in a current family. This was further supported by Benedetto in 1973, who named for the taxa the new family Herrerasauridae, which he classified as saurischians, possibly within Theropoda but not in Sauropodomorpha. However, in 1977 Galton proposed that Herrerasauridae only included "Herrerasaurus", and found it to be Saurischian "incertae sedis".