Riojasuchus tenuisceps (Bonaparte 1969) Late Triassic, 2 m in length, was derived from a sister to Euparkeria and was a sister to Ornithosuchus.
Distinct from Ornithosuchus, the skull or Riojasuchus had a more exaggerated premaxilla, which raised a slight bump on the dorsal rostrum. The antorbital fenestra was reduced by the expansion of the fossa. The lacrimal and postorbital processes of the jugal fused below the upper portion of the orbit. The mandibular fenestra was smaller.
The neural spines were all taller. The atlas (2nd cervical) was double the length of the others.
The pectoral girdle and forelimb were more robust.
The hind limbs were likewise more robust. The fibula was half the diameter of the tibia and included a short anterior process at midlength. The calcaneal "heel" was less well-developed. The pedal digits were relatively shorter. Metatarsal III was longer than IV.