Open Paleo

Riojasauridae

Yates, 2007 Type genus Riojasaurus

Its genera lived 227.3–201.4 million years ago Late Triassic
Late Triassic stages

Riojasauridae is a small family of sauropodomorph dinosaurs that lived during the Late Triassic, from the late Carnian into the Norian. It contains only two genera, Riojasaurus and Eucnemesaurus, whose fossils come from the Los Colorados Formation of La Rioja Province, Argentina, and the Lower Elliot Formation of South Africa, respectively. As sauropodomorphs rather than true sauropods, these were heavily built, medium- to large-bodied plant-eaters that were much smaller than the giant sauropods of later periods and may not have been fully committed to walking on all fours. The group is defined as a stem lineage within Massopoda, an early radiation of long-necked herbivores. Its precise placement remains unsettled: Barrett and colleagues (2024) recover it at the base of Massopoda, below the massospondylids, whereas Peyre de Fabrègues and colleagues (2020) place it crownward of Massospondylidae, nearer the sauropod line.

Diagnosis

  1. Tall crest-like lesser (anterior) trochanter of the femur, higher than wide
  2. Large posterior proximal tubercle on the femur
  3. Rounded, convex profile of the fourth trochanter of the femur
  4. Heavily built, weight-bearing postcranium

Genera placed directly in Riojasauridae

  • Eucnemesaurus Disputed Van Hoepen, 1920 Norian–Rhaetian (227.3–201.4 Ma)South Africa
  • Riojasaurus Bonaparte, 1969 Norian (227.3–205.7 Ma)Argentina

References

  1. Yates, A. M. (2007). Solving a dinosaurian puzzle: the identity of Aliwalia rex Galton. Historical Biology 19(1): 93-123. doi:10.1080/08912960600866953

    Erected Riojasauridae.

    yates2007a
  2. Barrett, P.; Chapelle, K.; Sciscio, L.; Broderick, T.; Zondo, M.; Munyikwa, D.; Choiniere, J. (2024). A new sauropodomorph dinosaur from the Late Triassic of the Mid-Zambezi Basin, Zimbabwe. Acta Palaeontologica Polonica 69. Polska Akademia Nauk Instytut Paleobiologii (Institute of Paleobiology, Polish Academy of Sciences). doi:10.4202/app.01100.2023

    Recovered Riojasauridae among the earliest-branching massopodans, below massospondylids and sauropodiforms.

    barrett2024a
  3. Peyre de Fabrègues, C.; Bi, S.; Li, H.; Li, G.; Yang, L.; Xu, X. (2020). A new species of early-diverging Sauropodiformes from the Lower Jurassic Fengjiahe Formation of Yunnan Province, China. Scientific Reports 10(1). Springer Science and Business Media LLC. doi:10.1038/s41598-020-67754-4

    Recovered Riojasauridae crownward of Massospondylidae and the Lufeng genera, nearer Sauropoda.

    peyredefabrègues2020a