Paleontologists in Patagonia, Argentina, have unearthed a portion of a postcranial skeleton that belonged to a previously unknown rebbachisaurid sauropod dinosaur.
Life reconstruction of Astigmasaura genuflexa. Image credit: Mattia Yuri Messina.
The newly-discovered dinosaur lived in what is now Argentina during the Late Cretaceous epoch, approximately 95 million years ago.
Scientifically named Astigmasaura genuflexa, the species was about 18 m (59 feet) long and weighed more than 10 tons.
The ancient giant was a member of Rebbachisauridae, a large family of sauropod dinosaurs within the superfamily Diplodocoidea.
“Rebbachisaurids are medium to large-sized, non-selective and ground-level browser diplodocoid sauropods, and they are characterized by highly specialized skulls, widely pneumatized axial elements and gracile appendicular skeletons,” said
“Known from the Early Cretaceous to the early Late Cretaceous, the rebbachisaurid fossil record is particularly diversified in the ancient supercontinent Gondwana, with several specimens found in North Africa and South America.”
“Notably, Patagonia has yielded over more than half of all known Rebbachisauridae, including the earliest forms and the youngest rebbachisaurid remains to date.”
Fieldwork at the El Orejano locality of the Huincul Formation in Patagonia, Argentina. Image credit: Flavio Bellardini.
The fossilized remains of Astigmasaura genuflexa were found at the El Orejano locality of the Huincul Formation in the Neuquén Basin, Patagonia, Argentina.
“The type material of Astigmasaura genuflexa comprises the posterior portion of an articulated, postcranial skeleton of a single, morphologically adult individual,” the paleontologists said.
The new species was one of the last rebbachisaurid dinosaurs before their extinction 90 million years ago.
“Astigmasaura genuflexa shares different conditions with other Rebbachisauridae, including anterior caudal vertebrae with tall neural spines and tetraradiate neural laminae, asymmetric middle haemal arches, mediolaterally compressed proximal tibiae, and femur with medially inclined distal condyles,” the researchers said.
“Furthermore, Astigmasaura genuflexa shows a unique combination of diagnostic features that distinguish it from all other sauropods.”
“This new record not only provides new morphological information about the caudal and pelvic girdle anatomy of Rebbachisauridae, which is poorly known to date, and suggests a greater taxonomic diversification within the family during the last stages of its evolutionary history than known before.”
The team’s paper published online in the journal Cretaceous Research.
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Flavio Bellardini et al. 2025. Side by side with titans: A new rebbachisaurid dinosaur from the Huincul Formation (upper Cenomanian) of Patagonia, Argentina. Cretaceous Research 176: 106188; doi: 10.1016/j.cretres.2025.106188