Riojasaurus

Riojasaurus was an exceptionally large basal sauropodomorph that inhabited South America during the Late Triassic, roughly 220 to 210 million years ago. Discovered in the arid red beds of the Los Colorados Formation in La Rioja Province, Argentina, it reached lengths of up to ten metres and weighed several tonnes. Unlike bipedal contemporaries such as Plateosaurus, Riojasaurus possessed dense, robust limb bones and equalised proportions that made it an obligate quadruped, incapable of rearing for sustained periods. Its neck was long and flexible, ending in a relatively small skull filled with leaf-shaped, serrated teeth adapted for cutting tough vegetation. Riojasaurus represented an early evolutionary experiment in massive body size among herbivorous dinosaurs, preceding the true sauropods of the Jurassic.

Unlike many contemporaneous sauropodomorphs, Riojasaurus was an obligate quadruped with heavy, solid limb bones.

Where and when

Riojasaurus lived in the Late Triassic, from 220 to 210 million years ago (Norian age). Its remains come from Argentina, in the Los Colorados Formation.

The numbers

Length 9 m (estimates run from 8 to 10 m). Mass about 2.6 t. Hip height about 2.5 m. That is 5.3 human-lengths, or 0.8 of a double-decker bus. These are estimates from near-complete skeleton; fields marked estimated by the site are length, mass, hip height.

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