The holotype specimen, PVL 3827, was found in the Los Colorados Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina.

They are listed below:[3] Riojasuchus is a member of Ornithosuchidae, a family of facultatively bipedal carnivores that were geographically widespread during the Late Triassic.

[1] Below is a phylogenetic cladogram by Butler et al. in 2011 showing the cladistics of Archosauriformes, focusing mostly on Pseudosuchia:[7] Clade names follow Nesbitt 2011.

[8] Mesosuchus Prolacerta Proterosuchus Erythrosuchus Vancleavea Tropidosuchus Chanaresuchus Euparkeria Parasuchus Smilosuchus Pseudopalatus Riojasuchus Ornithosuchus Gracilisuchus Turfanosuchus Revueltosaurus Aetosaurus Stagonolepis Longosuchus Ticinosuchus Qianosuchus Arizonasaurus Xilousuchus Hypselorhachis Ctenosauriscus Waldhaus Taxon Poposaurus gracilis H Poposaurus gracilis Y Lotosaurus Sillosuchus Shuvosaurus Effigia Prestosuchus Saurosuchus Batrachotomus Fasolasuchus Rauisuchus Polonosuchus silesiacus Postosuchus alisonae Postosuchus kirkpatricki

[1] It lived alongside the protosuchid Hemiprotosuchus; the sphenosuchid Pseudohesperosuchus; the stagonolepidid Neoaetosauroides; the melanorosaurid Strenusaurus; and the riojasaurid Riojasaurus.