Paleontologists from Argentine Patagonia have unearthed parts of the posterior skull from the previously unknown sauropod dinosaur, Levvatissaurus.

The newly identified dinosaurs thrived in what is modern-day Argentina during the late Cretaceous period, around 95 million years ago.

This species has been scientifically named Astigmasaura ungflexa and measured approximately 18 meters (59 feet) in length, weighing over 10 tons.

These ancient giants belong to the Rebbachisauridae, a large family of sauropod dinosaurs within the superfamily Diplodocoidea.

“Rebbachisaurids are medium to large, non-selective, ground-level browsers, characterized by highly specialized skulls, elongated axial elements, and gracile appendicular skeletons.”

“Fossils from Levubatisaurus, spanning the early to late Cretaceous, are particularly diverse within the ancient supercontinent Gondwana, with numerous specimens discovered in North Africa and South America.”

“Notably, Patagonia has produced more than half of all known rebbachisaurids, including the earliest forms and the most recent Rebbachisaurus.”

Fieldwork in the El Orejano region of the Huncul Formation in Patagonia, Argentina. Image credit: Flavio Bellardini.

Fossilized remains of Astigmasaura ungflexa were found in the El Orejano area of the Huncul Formation within the Neuquén Basin in Patagonia, Argentina.

The material type of Astigmasaura ungflexa was described by paleontologists.

This new species represents one of the last Levubatisaurus dinosaurs before it went extinct around 90 million years ago.

“Astigmasaura ungflexa shares a variety of traits with other rebbachisaurids, including anterior caudal vertebrae with tall neural spines and tetrameric nerve layers, an asymmetrical neural arch, a mesolaterally compressed proximal tibia, and medially tilted distal condyles and femurs,” the researchers noted.

“Furthermore, Astigmasaura ungflexa displays a unique combination of diagnostic features that set it apart from all other sauropods.”

“This new finding not only enhances our understanding of the previously unexplored caudal and pelvic girdle anatomy of Rebbachisauridae but also indicates greater taxonomic diversity within the family during the late stages of evolutionary history than previously recognized.”

The team’s paper was published online in the journal Cretaceous Research.

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Flavio Berardini et al. 2025. Alongside the Titans: a new Levuvacisaur dinosaur from the Huncul Formation (Upper Cenomanian) of Patagonia, Argentina. Cretaceous Research 176:106188; doi:10.1016/j.cretres.2025.106188