Researchers working in Argentina have discovered a new long-necked, plant-eating titanosaur. The 95-million-year-old Sarmientosaurus musacchioi had well developed sensory capabilities and a habitually downward-facing snout. It’s described in PLOS ONE this week. 

Titanosaurs were some of the largest vertebrates to ever walk the planet. They were a type of sauropod dinosaur that was extremely diverse and abundant during the Cretaceous, and their fossils have been discovered around the world. However, their skulls have rarely been found. There are at least 60 recognized titanosaurs, but only four of them are represented by nearly complete or even reasonably complete skulls. 

Now, using CT imaging, a team led by Rubén Martínez of Universidad Nacional de la Patagonia San Juan Bosco was able to study what they describe as a “superbly-preserved adult skull” that was still articulated with associated bones. The near-complete skull, neck vertebrae, and the right rib of the anatomically primitive titanosaur was unearthed from Upper Cretaceous sandstone in the Bajo Barreal Formation of south-central Chubut Province in central Patagonia. 

^{CT-based digital visualizations of the Sarmientosaurus skull with reconstructed brain endocase (purple), inner ear (pink), and eye. It's shown here with its inferred habitual head posture. Martínez RDF et al., PLoS ONE 2016}

The 43-centimeter-long (16.9-inch) cranium likely housed a small brain relative to its gigantic body – which was typical of sauropods. Although, the team did find evidence of sensory capabilities that may have been better than most other sauropods: Giant eye orbits suggest they had good vision, and the shape of their inner ear suggests they were well-tuned for hearing lower frequency airborne sounds. 

Additionally, the inner ear also indicates that Sarmientosaurus habitually held its head with the snout facing downwards around 46 degrees. This downturned head posture likely helped the giants feed on plants that grew low to the ground. Using its robust teeth, the dinosaur sliced up flowering plants, ferns, horsetails, and cycads. 

The new genus name combines “Sarmiento,” for the area it was discovered in, with “saurus,” Greek for lizard. The species name honors the late Eduardo Musacchio of Universidad Nacional de la Patagonia San Juan Bosco.

^{Life reconstruction of Sarmientosaurus musacchioi in its 95-million-year-old habitat in southern Chubut Province, central Patagonia, Argentina. Mark A. Klingler/Carnegie Museum of Natural History & WitmerLab/Ohio University}