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Riojasaurus

Bonaparte, 1969 ree-OH-hah-SAWR-us

Named after La Rioja Province in Argentina where it was found, combined with Greek sauros (lizard); meaning "lizard from La Rioja".

227.3–205.7 million years ago Norian, Late Triassic
Late Triassic stages

Riojasaurus was a herbivorous sauropodomorph dinosaur named after La Rioja Province in Argentina where it was found in the Los Colorados Formation in the Ischigualasto-Villa Unión Basin by José Bonaparte. It lived during the Late Triassic (Norian stage) and grew to about 6.6 meters (22 ft) long. Riojasaurus is the only known riojasaurid to live in South America.

Diagnosis

  1. Femur relatively straight in dorsal view
  2. Femoral head projects medially, forming a right angle with the shaft
  3. Humerus robust, with a broad internal tuberosity and deltopectoral crest, and a short diaphysis constrained by the proximal and distal expansions
  4. Ilium robust, with a broad posterior projection, the preacetabular process only slightly longer than the postacetabular process
  5. Pubis with straight lateral and medial edges
  6. Tibia plus astragalus length equal to 90% of femur length, humerus equal to 80% of femur length, and humerus plus radius equal to 67% of femur plus tibia length

Species

Riojasaurus incertus Bonaparte, 1969

Type species

From Latin 'incertus' meaning 'uncertain' or 'doubtful'.

Holotype
PVL 3808 , Colección de Paleontologia de Vertebrados de la Fundación Instituto Miguel Lillo
Material
Most of a postcranial skeleton, lacking any cranial remains.
Horizon
upper Los Colorados Formation, Norian, Late Triassic , 227.3–205.7 million years ago
Locality
La Rioja, Argentina

Synonyms of the genus

Name Type Reason
Strenusaurus junior subjective Now interpreted as a juvenile specimen of Riojasaurus.

References

  1. Bonaparte, J. F. (1969). Dos nuevas "faunas" de reptiles triasicos de Argentina [Two new reptilian "faunas" of the Argentine Triassic]. Gondwana Stratigraphy (IUGS Symposium, Buenos Aires) 2: 283-306. bonaparte1969a
  2. Jones, B. (2026). The Princeton Encyclopedia of Dinosaurs: Sauropods. Princeton University Press.

    Source of the hip height estimate, and the appearance features.

    jones2026b