Paleontologists have unearthed fossilized bones of one of the smallest known sauropodomorph dinosaurs from the Late Triassic period in southern Brazil, offering new insights into the early growth strategies and development of these creatures that would eventually become the largest land animals to ever walk the Earth.
The discovery, detailed in research slated for publication in the April 2026 issue of the journal Palaeoworld, centers around remarkably small bones – all less than 5.7 cm (2.2 inches) in length – recovered from the Cerro da Alemoa outcrop in Rio Grande do Sul, Brazil. The bones include a partial humerus, a metatarsal, an ungual phalanx, a neural arch, and a vertebral centrum.
Dr. Luciano Artemio Leal from the Universidade Estadual do Sudoeste da Bahia led the team responsible for the analysis. According to the researchers, the Cerro da Alemoa outcrop is a crucial site for understanding the region’s Late Triassic fauna, representing a key record of the Santa Maria Supersequence.
Phylogenetic and anatomical analyses firmly place the specimen within the basal sauropodomorph clade, meaning it represents an early branch in the evolutionary tree of these long-necked herbivores. Importantly, the fossil represents a juvenile dinosaur, still undergoing development.
The significance of this find lies in the bone microstructure. Researchers observed evidence of at least one complete cycle of growth interruption, marked by a line of arrested growth. This suggests the young dinosaur experienced pauses in its development – a finding that challenges previous assumptions about how these early dinosaurs grew.
“The observed features suggest an individual still in development, having already undergone its first growth arrest and being midway through its second cycle,” the researchers explained in their forthcoming publication.
This pattern of interrupted growth is particularly intriguing because it indicates that even at a diminutive size, early sauropodomorphs were already exhibiting flexible growth strategies. This flexibility may have been a crucial precursor to the gigantism that characterized later sauropodomorphs like Brachiosaurus and Argentinosaurus.
The discovery adds to a growing body of evidence suggesting that elevated growth rates were a key factor in the success of dinosaurs. Research published in 2024, examining fossils from the Ischigualasto Formation in Argentina, indicated that early dinosaurs grew relatively quickly compared to their contemporaries, including synapsids and pseudosuchians. This rapid growth may have allowed them to outcompete other tetrapod groups in the aftermath of the Permian-Triassic extinction event, a period of significant environmental upheaval.
The Permian-Triassic extinction, often called the “Great Dying,” wiped out approximately 95% of all life on Earth roughly 252 million years ago. The subsequent Triassic period saw the rise of new groups of animals, including the ancestors of dinosaurs. While dinosaurs initially represented a small fraction of the ecosystem, they eventually came to dominate terrestrial environments.
The late Triassic period wasn’t without its own challenges. Another extinction event, though less severe than the Permian-Triassic, occurred around , further shaping the evolutionary landscape. The ability to grow quickly may have given dinosaurs an advantage in recovering from these environmental stresses.
The Brazilian fossil provides a rare glimpse into the early stages of this evolutionary process. By studying the bone microstructure of this juvenile sauropodomorph, paleontologists are gaining a better understanding of how these animals developed and adapted to their environment. The findings suggest that the foundations for the immense size of later sauropodomorphs were laid much earlier than previously thought, with flexible growth strategies emerging even in these small, early forms.
“Our results provide evidence for novel growth strategies during the early evolution of this group, leading to the emergence of small-bodied dinosaurs in the Triassic,” the researchers concluded.
