Paleontologists have discovered a new collection of Triassic fossils at the Quebrada Santo Domingo site in the northern Pre-Cordillera Basin of northwestern Argentina. Among their findings are nearly complete skeletons of a previously unknown sauropod dinosaur species, along with several cynodonts, rhinocosaurs, and aetosaurs.

The newly identified species existed in what is now Argentina during the Carnian period of the late Triassic, approximately 230 million years ago.

Known as Huayracursor jaguensis, this dinosaur was an early and primitive member of the clade sauropodomorpha.

The ancient creature featured a relatively long neck and was larger than many of its contemporaries.

“The Carnian period (237 to 227 million years ago) is significant in the evolution of tetrapods, holding the earliest records of several major clades, including dinosaurs,” stated paleontologist Dr. Martin Hechenleitner of the La Rioja Regional Research Center and CONICET, along with colleagues.

“Following the Carnian pluvial period, dinosaurs faced unprecedented radiation levels and quickly established dominance for the remainder of the Mesozoic era.”

“Most of the earliest records originate from a few well-researched regions in South America, specifically the Izquiguarasto-Villa Union Basin in western Argentina and the Paraná Basin in southern Brazil.”

“These locales have produced a variety of early dinosaurs, encompassing ornithischians, herrerasaurs, theropods, and sauropods.”

“While sauropods are the most taxonomically diverse, the majority (with a few fragmentary exceptions) were small, bipedal, and short-necked.”

“Despite the advances in our understanding of the quadrupedal fauna from the Carnian, no dinosaur-containing groups have arisen outside of traditional classifications.”

Selected bone of the Huayracursor jaguensis holotype. Image credit: Hechenleitner et al., doi: 10.1038/s41586-025-09634-3.

Dr. Hechenleitner and his co-authors uncovered fossilized remains of Huayracursor jaguensis and other Triassic animals in the Santo Domingo formation at Quebrada Santo Domingo, a remote region of the Andes Mountains in La Rioja, northwestern Argentina.

“This newly discovered fauna is the first from the newly characterized northern Pre-Cordillera Basin,” the paleontologists remarked.

“Current findings encompass ceratopsians of the hyperodapedontid family, cynodonts from the traversodontid and probynognathic families, a eurysaurian, and at least two sauropod dinosaurs, indicating a Carnian age.”

“Among the sauropods, Huayracursor jaguensis provides the earliest evidence of concurrent weight gain and neck elongation in sauropods, suggesting that these crucial traits emerged at the dawn of dinosaurs.”

“This discovery enhances our understanding of the diversity and geographic distribution of early dinosaur faunas and illuminates the evolution of sauropods during the Carnian period.”

The findings regarding Huayracursor jaguensis are detailed in a paper published in the journal Nature.

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EM Hechenleitner et al. A newly discovered long-necked early dinosaur from the Upper Triassic basin of the Andes. Nature, published online October 15, 2025. doi: 10.1038/s41586-025-09634-3