New genus and species of theropod dinosaurs named Anteavis crrilongus was described by a team of paleontologists from the National University of San Juan, the Argentine Museum of Natural Sciences Bernardino Rivadavia, the University of Birmingham, CONICET and CIGEOBIO.
Anteavis crrilongus roamed the Earth during the Carnian era of the Late Triassic, 231–226 million years ago.
This dinosaur was approximately 1.2 m (4 ft) long and weighed about 8-9 kg.
The ancient species was an early divergent theropod outside the dinosaur group. neotheropodsbut it unexpectedly gained features that were previously considered exclusive to this group.
“This is one of the oldest and most primitive dinosaurs known to date,” said Dr. Ricardo Martinez from the National University of San Juan and his colleagues.
“The early diversification of dinosaurs led to major ecological changes in terrestrial ecosystems, culminating in the emergence of dinosaur-dominated tetrapod aggregations at the Triassic-Jurassic boundary 201 million years ago.”
“Studying the initial diversification of dinosaurs is therefore critical to understanding the formation of Mesozoic assemblages.”
“However, the lack of stratigraphically continuous fossil data in the few geological units that preserved the oldest known dinosaurs (233-227 million years ago) clouds our understanding of this initial diversification.”
Paleontologists have discovered fossilized remains Anteavis crrilongus – partial skeleton and skull – in the Ischigualasto Formation in northwestern Argentina in 2014.
“There are very few places in the world that have such ancient and well-preserved fossils,” Dr. Martinez said.
“One is the Santa Maria Formation in the Brazilian state of Rio Grande do Sul, the other is the Ischigualasto Formation.”
Anteavis crrilongus lived in a warm and dry savannah about two million years after Rain episode.
“We show that dinosaur diversity and abundance in the Ischigualasto Formation were higher than previously thought, especially among small herbivores (<30 kg) and medium-sized carnivores (30–200 kg),” the researchers said.
“This diversification occurred at Ischigualasto during a climatic transition to semi-arid conditions, but the return to wetter conditions resulted in a gap in the dinosaur record that began approximately 229 million years ago.”
“It was not until 15 million years later, during the Middle Norian period, that dinosaurs regained their numbers and diversity in the basin, but were now characterized by larger species.”
“Our results demonstrate early dinosaur diversification, likely accentuated by climate-driven faunal turnover in at least southwestern Pangea.”
A paper The discovery was published this week in the magazine Ecology of nature and evolution.
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R.N. Martinez etc.. A Carnian theropod with unexpected features during the first radiation of dinosaurs. Nat Ecole Evolpublished online October 14, 2025; doi: 10.1038/s41559-025-02868-4
