Researchers from CONICET and national institutions found in the north of the province of Neuquén the fossil remains of a new species of sauropod dinosaur. It belongs to the group of rebaquisaurids, which lived in the region approximately 95 million years ago.
The discovery was recently published in the journal Cretaceous Research.
The species was named Astigmasaura genuflexa. It was a large herbivorous quadruped, reaching 18 meters in length and weighing over 10 tons. It had a long neck and tail, slender legs, and a bony structure in the tail with vertebrae and haemal arches of unique morphologies, including boot and star shapes.
Discovery and excavation: an almost complete fossil
The discovery was made in 2017 following an accidental report by oil workers at the GASNOC YPF El Orejano field, within the lower levels of the Huincul Formation.
As reconstructed by paleontologists, the remains were transported by a low-energy river and got stranded on a sandy bar. A sudden flood allowed for the partial preservation of the skeleton, especially of the rear part.
The team led by Flavio Bellardini, a postdoctoral fellow at CONICET in the Institute of Research in Paleobiology and Geology (IIPG, CONICET–UNRN), carried out five paleontological campaigns and over 30 days of fieldwork. The recovery of the material required manual tools and heavy machinery to extract the eight large plaster jackets protecting the bones.
A new dinosaur species key to understanding the evolution of rebaquisaurids
Astigmasaura becomes the first rebaquisaurid species with both hind limbs, the hip, and part of the tail perfectly preserved. This allowed for the first reconstruction of the posterior anatomy of these sauropods.
The discovery includes elements such as complete feet and muscular structure, essential for studies on locomotion, posture, and fossil traces.
In addition, the fossils showed particular ossifications in tendons and vertebral pathologies, indications that the specimen was of advanced age at the time of its death.
Meaning of the name: a “ownerless”, kneeling dinosaur
The genus name, Astigmasaura, comes from the Latin a- (without) and stigma (marks), alluding to El Orejano, a popular expression referring to an animal without signs of ownership. The epithet genuflexa refers to the position in which the specimen was found: with both hind legs bent, as if kneeling.
Subsequent anatomical study allowed for the comparison of its features with those of other South American species in the group. Astigmasaura would have been one of the last representatives of the rebaquisaurid lineage before its extinction, about 90 million years ago, giving it a key value in understanding the last evolutionary phases of these dinosaurs in Patagonia.
