Paleontologists have discovered a new assemblage of Triassic fossils at the Quebrada Santo Domingo site in the northern Precordillera basin in northwestern Argentina. Their discoveries include a nearly complete skeleton of a previously unknown species of sauropodomorph dinosaur as well as several cynodonts, rhynchosaurs and aetosaurs.
Huayracursor jaguensis. Image credit: Jorge Blanco.
The newly discovered species lived in what is now Argentina during the Carnian period of the late Triassic, around 230 million years ago.
Appointed Huayracursor jaguensisthis dinosaur was an early and primitive member of the Sauropodomorpha clade.
The ancient animal had a considerably longer neck and was larger than most of its contemporaries.
“The Carnian age (237 to 227 million years ago) marks a crucial interval in the evolution of tetrapods, preserving the earliest records of several major clades, including dinosaurs,” said Dr. Martin Hechenleitner, a paleontologist at the Centro Regional de Investigaciones Científicas y Transferencia Tecnológica de La Rioja and CONICET, and his colleagues.
“After the Carnian Pluvial Episode, dinosaurs underwent significant radiation, quickly establishing their dominance for the remainder of the Mesozoic era.”
“Most of the early records come from a small number of well-studied localities in South America, in the Ischigualasto-Villa Unión Basin in western Argentina and the Paraná Basin in southern Brazil.”
“These sites yielded diverse early dinosaurs, including ornithischians, herrerasaurids, theropods and sauropodomorphs.”
“Although sauropodomorphs were the most taxonomically diverse, almost all were (with a few exceptions) small, short-necked bipedal forms.”
“Despite advances in our understanding of Carnian tetrapod faunas, no dinosaur assemblages have emerged outside of traditional units.”
Selected bones from Huayracursor jaguensis holotype. Image credit: Hechenleitner and others., doi: 10.1038/s41586-025-09634-3.
Dr. Hechenleitner and his co-authors discovered the fossilized remains of Huayracursor jaguensis and several other Triassic animals in the Santo Domingo Formation at Quebrada Santo Domingo, an isolated locality in the Andes of La Rioja Province, northwest Argentina.
“This new fauna is the first to be recovered from the newly identified northern Precordillera Basin,” the paleontologists said.
“Current discoveries include hyperodapedontic rhynchosaurs, traversodontid and probainognathian cynodonts, aetosaurs, and at least two sauropodomorph dinosaurs, indicating a Carnian age.”
“Among the sauropodomorphs, Huayracursor jaguensis provides the first evidence of a synchronous increase in body mass and neck elongation in Sauropodomorpha, suggesting that these key traits emerged at the dawn of the dinosaurs.
“This discovery expands the known diversity and geographic distribution of early dinosaur faunas and broadens our understanding of the evolution of sauropodomorphs in the Carnian Age.”
The discovery of Huayracursor jaguensis is described in an article in the journal Nature.
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EM Hechenleitner and others. A primitive, long-necked dinosaur from a recently discovered Late Triassic basin in the Andes. Naturepublished online October 15, 2025; doi: 10.1038/s41586-025-09634-3
