Rocasaurus

Rocasaurus was a diminutive titanosaur sauropod from the Late Cretaceous of northern Patagonia, Argentina. Found in the Allen Formation near the city of General Roca, it reached merely eight to nine metres in total length and weighed roughly three tonnes, making it dwarfed by most of its sauropod relatives. Despite its modest size, Rocasaurus was a robustly built quadruped equipped with bony dermal armour plates embedded in its skin for defence. Anatomically, its tail vertebrae display notable lateral depressions and internal hollows, an adaptation that lightened its skeleton while maintaining structural strength. Rocasaurus lived alongside other small saltasaurines such as Saltasaurus and Neuquensaurus, demonstrating that specialised small-bodied titanosaurs flourished across South America right up until the end of the Cretaceous period.

It is one of the smallest known sauropods, exhibiting pneumatic cavities in its tail vertebrae to reduce bone weight.

Where and when

Rocasaurus lived in the Late Cretaceous, from 72.1 to 66 million years ago (Maastrichtian age). Its remains come from Argentina, in the Allen Formation.

The numbers

Length 8.5 m (estimates run from 8 to 9 m). Mass about 3.2 t. Hip height about 2 m. That is 5 human-lengths, or 0.76 of a double-decker bus. These are estimates from partial skeleton; fields marked estimated by the site are length, mass, hip height.

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