In 1981, Mourer-Chauviré redescribed S. minor as Ameghinornis minor, the only member of the new phorusrhacid subfamily, Ameghinornithinae. Ameghinornis was later placed in its own family, Ameghinornithidae. In 1987, Peters named another monospecific genus of ameghinornithid, Aenigmavis sapea, based on a nearly complete skeleton from the Middle Eocene Messel pit of Germany.
In 1981, Mourer-Chauviré redefined S. minor as Ameghinornis minor, establishing it as the sole member of the new phorusrhacid subfamily, Ameghinornithinae. Later, Ameghinornis was recognized as its own family, Ameghinornithidae. In 1987, Peters introduced Aenigmavis sapea, a monospecific genus of ameghinornithid, based on a nearly complete skeleton from the Messel pit in Germany during the Middle Eocene period.