A novel genus and species of theropod dinosaur, christened Anteavis crurilongus, has been formally identified and detailed by a collaborative team of paleontological experts affiliated with the Universidad Nacional de San Juan, the Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia,’ the University of Birmingham, CONICET, and CIGEOBIO.
An artist’s reconstruction of Anteavis crurilongus. Image credit: Jorge Blanco.
Anteavis crurilongus navigated this planet during the Carnian stage of the Late Triassic period, a span of time between 231 and 226 million years ago.
This remarkable creature attained a physical stature of approximately 1.2 meters (4 feet) in length and possessed an estimated mass of about 8-9 kilograms.
The ancient creature represents an early offshoot of theropods, positioned outside the taxonomic classification of Neotheropoda. However, it exhibited surprisingly advanced traits, features that were hitherto believed to be exclusively characteristic of that particular lineage.
“It stands as one of the most ancient and rudimentary dinosaurs discovered to date,” stated Dr. Ricardo Martínez of the Universidad Nacional de San Juan, alongside his research colleagues.
“The initial proliferation of dinosaurs triggered a profound ecological transformation within terrestrial biomes, culminating in terrestrial faunal communities overwhelmingly dominated by dinosaurs by the advent of the Triassic/Jurassic boundary, approximately 201 million years ago.”
“Consequently, scrutinizing the nascent diversification of dinosaurs is paramount for comprehending the foundational establishment of Mesozoic faunal assemblages.”
“Nevertheless, the scarcity of stratigraphically coherent fossil evidence unearthed from the geological strata that harbor the planet’s oldest known dinosaurs (dating back 233-227 million years ago) impedes a comprehensive understanding of this initial evolutionary expansion.”
The fossilized remains of Anteavis crurilongus—comprising a partial skeleton and cranial elements—were exhumed by the paleontologists from the Ischigualasto Formation, located in northwestern Argentina, during excavations conducted in 2014.
“The global repository of exceptionally ancient and exquisitely preserved fossil specimens is exceedingly limited,” Dr. Martinez remarked.
“One such invaluable site is the Santa Maria Formation in Brazil’s Rio Grande do Sul state; another is the Ischigualasto Formation.”
Anteavis crurilongus inhabited a savanna environment characterized by warm and arid conditions, existing approximately two million years following the Carnian pluvial episode.
“Our research indicates that the prevalence and variety of dinosaurs within the Ischigualasto Formation were greater than previously estimated, particularly among diminutive herbivores (weighing less than 30 kg) and mesopredators (ranging from 30-200 kg),” the researchers elaborated.
“This evolutionary surge occurred within the Ischigualasto region during a climatic transition towards semi-arid conditions. However, a subsequent return to more temperate, humid climates resulted in a hiatus in the dinosaur fossil record, commencing around 229 million years ago.”
“A mere 15 million years thereafter, during the mid-Norian epoch, the dinosaur record re-emerged with renewed abundance and diversity within the basin, though it was now characterized by species of appreciably larger stature.”
“Our findings provide compelling evidence for an early dinosaur radiation, likely influenced by climate-induced faunal shifts, at least within the southwestern sector of the supercontinent Pangea.”
A comprehensive scientific publication detailing this discovery was released this week in the esteemed journal Nature Ecology & Evolution.
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R.N. Martínez et al. A Carnian theropod with unexpectedly derived features during the first dinosaur radiation. Nat Ecol Evol, published online October 14, 2025; doi: 10.1038/s41559-025-02868-4
