Lost Triassic Fossil Unearthed in Brazil Redraws Dinosaur Family Tree

A fragmentary fossil discovered in the rocks of the UNESCO Quarta Colônia Geopark in central Rio Grande do Sul has been formally described as a new species, Silescelida acristata, dating to about 240 million years ago in the Middle Triassic. The animal was a small, slender predator with four limbs, comparable in size to a tiny alligator, and its femur shows a semi-erect stance that hints at the locomotor innovations later seen in archosaurs.

Researchers from the Quarta Colônia Center for Paleontological Research at the Federal University of Santa Maria, together with colleagues from the Federal University of Rio Grande do Sul and the Pontifical Catholic University of Rio Grande do Sul, used the rediscovered limb fragment to confirm its provenance and phylogenetic ties to the Euparkeriidae, a group previously known only from Africa, Asia and Europe. This South American occurrence expands the known distribution of those early archosauriforms and underscores the continent's importance for studying the origins of dinosaurs and crocodiles. The study, published in Scientific Reports, highlights how even incomplete fossils can provide critical insights into evolutionary history.