Source of comparative data used in this study.

All comparative references to the following taxa have been observed in the listed specimens or taken from the respective bibliographic reference. Comparisons based on other specimens or taken from additional references are explicitly indicated in the text. BPI, Bernard Price Institute, Johannesburg, South Africa; IVPP, Institute of Vertebrate Paleontology and Paleoanthropology, Beijing, People's Republic of China; MB, Institut für Palaontologie, Museum fur Naturkunde, Humbolt-Universität, Berlin, Germany; MCP, Museu Pontifícia Universidade Católica, Porto Alegre, Brazil; NGMJ, Nanjing Geological Museum, Nanjing, People's Republic of China; NM QR, National Museum, Bloemfontein, South Africa; PVL, Instituto Miguel Lillo, Tucumán, Argentina; SAM, Iziko - South African Museum, Cape Town, South Africa; SMNS, Staatliches Museum für Naturkunde Stuttgart, Stuttgart, Germany; YPM, Yale Peabody Museum, New Haven, Connecticut, USA.