Some Sauropod Dinosaurs Stood Upright, Especially When Young

Two South American sauropod dinosaurs could stand on their hind legs for extended periods, particularly when young. This ability may have helped them access high foliage, deter predators, or attract mates. These findings come from a study supported by the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP).

The dinosaurs, *Uberabatitan* from Brazil and *Neuquensaurus* from Argentina, were roughly the size of modern elephants. *Uberabatitan* adults could reach up to 26 meters in length. Researchers suggest that their capacity to stand upright decreased with age.

Younger animals supported themselves more easily on two legs. Adults likely experienced greater strain due to their increased weight. The research team used computational methods common in engineering to analyze the stress on the dinosaurs' femurs, or thigh bones.

They created digital reconstructions of femurs from seven sauropod species. Finite element analysis (FEA) was used to simulate the forces of gravity and body weight on the femur. This method breaks a structure into small sections to calculate its response to pressure.

The lowest stress levels were observed in a juvenile *Uberabatitan ribeiroi* and *Neuquensaurus australis*. Both species lived approximately 66 million years ago during the Late Cretaceous period. Their robust femurs were better equipped to distribute the forces of standing upright.

While larger sauropods may have also stood on their hind legs, simulations indicate they could not maintain the posture as comfortably or for as long. The study acknowledges limitations, such as not modeling cartilage or tail support, but emphasizes the method's effectiveness for comparative analysis.