Paleontologists working in Brazil have identified a previously unknown species of archosauriform that lived around 240 million years ago and likely belongs to a poorly understood group of ancient reptiles that closely resembled the ancestors of crocodiles and dinosaurs. The research team’s findings were published in the journal Scientific Reports.
Silescelida acristata inhabited what is now Brazil during the Middle Triassic, a period when life on Earth was recovering and diversifying following the mass extinction at the end of the Permian era.
During this time, archosauriforms—a broader group of reptiles from which dinosaurs, pterosaurs, and crocodiles later evolved—began to dominate terrestrial ecosystems.
The newly discovered species likely belongs to the rare and still inadequately studied group of archosauriforms known as Euparkeriidae.
The most well-known member of the Euparkeriidae, Euparkeria capensis, was first described in South Africa in 1913 and remains the only reliably confirmed representative of this family.
“The Euparkeriidae family is primarily known from the emblematic stem archosaur Euparkeria capensis from the Early to Middle Triassic of South Africa and is currently the only definitively identified member of this clade,” stated lead study author Maurício Garcia from the Federal University of Santa Maria and his colleagues.
Other suspected euparkeriids come mainly from China and Europe.
In all major modern phylogenetic analyses of non-archosaurian archosauriforms, Euparkeria capensis and the Euparkeriidae have been placed in groups situated just outside Archosauria.
Consequently, this species, along with other presumed euparkeriids, holds great significance for understanding the origins of archosaurs, as it has long been regarded as close to the ancestral body plan of archosaurs.”
The skeletal remains of Silescelida acristata—a left scapula, a right pelvic bone, and a left femur (measuring approximately 17.3 cm in length)—were discovered at an excavation site in Posto, in the municipality of Dona Francisca, Rio Grande do Sul state, Brazil.
Based on comparisons with related animals, the new species likely resembled a long-legged, agile, lizard-like predator.
The discovery of Silescelida acristata expands the known geographic range of the euparkeriid lineage.
It also confirms that South America was a crucial region during the early stages of archosauriform evolution.
“This discovery not only provides information on the temporal and paleogeographic distribution of euparkeriids but also sheds light on the origin and early evolution of eucrocopods, representing the first report of this group of archosauriforms in the Triassic of Brazil,” the paleontologists concluded. “On a broader scale, the new species highlights the significance of South American Triassic deposits in the evolutionary history of archosauriforms.”
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