Scientists have found a 237 million-year-old fossil in Paraíso do Sul in southern Brazil. The fossilized creature was identified as a new species belonging to the “silesaurids,” one of the oldest archosaurs – a group of reptiles comprising the ancestors of crocodiles and birds. This fossil, dating back to the Middle-Upper Triassic, represents a historic discovery shedding light on dinosaur evolution, although opinions remain divided.
The research, led by paleontologist Rodrigo Temp Müller, describes the newfound species, Gondwanax paraisensis, as a reptile about the size of a dog with an elongated body and beak. It walked on four legs and resembled the earliest dinosaurs. Remarkably, it lived about 10 million years before the official appearance of dinosaurs.
All dinosaurs descended from a common ancestor from the Triassic era. It is unknown, however, where silesaurids fall in this evolution. While most paleontologists argue that the silesaurids were a sister group to dinosaurs rather than true dinosaurs, some hypothesize that certain silesaurids might have evolved into ornithischians, herbivorous dinosaurs with features similar to that of birds.
Scientists say understanding silesaurids could provide a deeper understanding of what physical traits made dinosaurs so successful. However, fossils of those likely related to ornithischians are rare and hard to identify due to missing crucial anatomical pieces.
The newly examined fossil, representing one of the oldest silesaurids ever found, may provide a crucial piece of the evolutionary puzzle. Gondwanax has dinosaur-like traits, suggesting it might have been a true dinosaur and a rare example of a Triassic ornithischian. If this hypothesis is confirmed, it would mean that herbivorous dinosaurs existed much earlier than previously thought, with a broader distribution.
This discovery could potentially rewrite the origin of dinosaurs and put Brazil on the map of countries with fossil records of precursor reptiles, geographically restricted to China and Argentina.