237-million-year-old mysterious fossil discovery could rewrite dinosaur history

Brazilian researchers discovered a 237-million-year-old reptile fossil that might be a precursor to the dinosaur, though only the size of a small dog.

As one of the world’s oldest fossils, they discovered a new species of silesaurids – an extinct family from the Late Triassic period.

As a previous study in the journal Nature states , this group, in particular, “is the main source of information regarding the ancestral plan of dinosaurs.” However, “the co-occurrence of silesaurs and the oldest dinosaurs are rare.”

Researchers have finally found the first species from Brazil’s oldest unequivocal dinosaur-bearing beds.

Whether or not they are dinosaurs remains a subject of debate, but the authors of the new study believe that this fossil and studying silesaurs can give the field new insights into the evolution of dinosaurs, and not just any dinosaurs, “the bird-line archosaurs.”

The Gondwanax paraisensi

In 2015, paleontologist Rodrigo Temp Muller found the Gondwanax paraisensi in the town of Paraiso do Sul in the south of Brazil on a rock that dates to the Triassic era. Different animals, such as dinosaurs and mammals, emerged at that time, as Reuters reports. But it wasn’t until 2021 that the research kicked off.

A new study just published in Gondwana Research, referring to the supercontinent that existed before the great separation into the continents we live on today, confirms one of the oldest dinosauromorphs has been identified. Specifically, it’s the earliest “silesaurid.” And it had some remarkable anatomical features that might reveal new insights into this unprecedented and unreachable moment in the history of evolution.

“The unique combination of sacral and hindlimb features may suggest distinct behaviors for these species, potentially leading to niche differentiation within the same ecosystems.”

Evidence suggests that “the precursors to the dinosaurs and pterosaurs were much more diverse than previously imagined.” Pterosaurs are flying reptiles, essentially. They evolved to be able to fly. And this species seems to provide insights, specifically, into the evolution of bird-line archosaurs, as this group encompasses both reptiles and birds.

The oldest silesaurid ever found

Silesaurids lived for 30 million years, but Gondwanax paraisensi is the oldest example ever found and a new species within this fascinating family.

Beyond the thrilling discovery, the study authors conclude that “it is crucial to understand their anatomy, biology, and evolution to investigate to faunal successions of the Triassic Period.”

So what will we learn about the evolution of the ancient beasts that spawned around this time?

Investigations regarding the early evolutionary history of bird-line archosaurs have undergone significant advancements in recent years. However, controversies remain, especially regarding the phylogenetic position of “silesaurids”. Whereas some hypotheses place these archosaurs as the sister-group to dinosaurs, others suggest that “silesaurids” are early ornithischian dinosaurs. Despite the phylogenetic disputes, “silesaurids” are a crucial group for comprehending the origins and early evolution of dinosaurs.

In the present study, a new “silesaurid” from the Middle-Upper Triassic of Southern Brazil is described. Gondwanax paraisensis gen. et sp. nov. comes from the Dinodontosaurus Assemblage Zone of the Santa Maria Formation (Ladinian-Carnian boundary), representing one of the oldest “silesaurids” worldwide. Furthermore, Gondwanax paraisensis gen. et sp. nov is the oldest “silesaurid” with three sacral vertebrae, a feature usually observed in more derived forms. In addition, distinct from any other Triassic Pan-Aves, the new taxon bears an incipient fourth trochanter of the femur. This unique combination of features indicates a high diversity of locomotor strategies among early pan-avians. The co-occurrence of Gondwanax paraisensis gen. et sp. nov. and Gamatavus antiquus in the same Assemblage Zone represents the oldest evidence of sympatry among “silesaurids” in South America. Indeed, the unique combination of sacral and hindlimb features may suggest distinct behaviors for these species, potentially leading to niche differentiation within the same ecosystems.