Genus: Ignotosaurus MARTINEZ, APALDETTI, ALCOBER, COLOMBI, SERENO, FERNANDEZ, MALNIS, CORREA & ABELIN, 2013
Etymology: Latin, ignotus, "unknown" and Greek, sauros, "lizard"; in reference to the previously unkonw presence of silesaurids in the well-sampled Ischigualasto Formation.

Species: fragilis MARTINEZ, APALDETTI, ALCOBER, COLOMBI, SERENO, FERNANDEZ, MALNIS, CORREA & ABELIN, 2013
Etymology: Latin, fragilis, "fragile"; in reference to the extremely thing central portion of the blade of the ilium and gracile proprotions of the femur.

Holotype: PVSJ 884

Locality: Along the northern edge of Cancha de Bochas, S30°06'51", W67°54'14", San Juan Province, Argentina.

Horizon: Base of the Ischigualasto Formation, lower portion of the Cancha de Bochas Member.

Biostratigraphy:

Age: Late Carnian Stage, Early Late Triassic Epoch, Lower Late Triassic.

Material: Right ilium.