Riojasauridae is an extinct clade of sauropodomorphdinosaurs from the Late Triassic epoch. It contains the generaRiojasaurus and Eucnemesaurus. It is a stem-based taxon, defined as "the most inclusive clade containing Riojasaurus incertus but not Plateosaurus engelhardti, Massospondylus carinatus, or Anchisaurus polyzelus".[1]Geologic formations containing riojasaurid fossils include the Lower Elliot Formation of Orange Free State, South Africa (where fossils of Eucnemesaurus have been found), and the Ischigualasto Formation, in La Rioja Province, Argentina (where fossils of Riojasaurus have been recovered).[1]
The cladogram below shows basal sauropodomorph relationships simplified after Yates, 2007. In this analysis, Riojasauridae was recovered as the earliest-diverging lineage of the clade Massopoda.[1]
The following cladogram is from a phylogenetic analysis by Peyre de Fabrègues et al., 2020. Here, Riojasauridae was placed in a more derived position, lying closer to Sauropoda than to Massospondylidae:[2]
^ abcYates, A. M. (2007). "Solving a dinosaurian puzzle: the identity of Aliwalia rex Galton". Historical Biology. 19 (1): 93–123. doi:10.1080/08912960600866953.
^Peyre de Fabrègues, C.; Bi, S.; Li, H.; Li, G.; Yang, L.; Xu, X. (December 2020). "A new species of early-diverging Sauropodiformes from the Lower Jurassic Fengjiahe Formation of Yunnan Province, China". Scientific Reports. 10 (1): 10961. doi:10.1038/s41598-020-67754-4.
