A recent study led by researchers from University College London (UCL) suggests that the remains of the earliest dinosaurs might still lie hidden in the Amazon and other equatorial regions of South America and Africa. This finding challenges previous conceptions about the origin of these creatures and raises new questions about their early evolution.

The oldest known dinosaur fossils date back approximately 230 million years and have been found further south, in places like Brazil, Argentina, and Zimbabwe. However, the differences observed among these fossils indicate that dinosaurs had already been evolving for millions of years before that time. This suggests that their origin could date even further back in history.

The study, published in the journal Current Biology, relied on models that accounted for gaps in the fossil record. According to the researchers, dinosaurs likely emerged in a warm, equatorial region of the Gondwana supercontinent, which at the time included areas now occupied by the Amazon, the Congo Basin, and the Sahara Desert.

Joel Heath, the study’s lead author and a doctoral student in Earth Sciences at UCL, noted:Although dinosaurs have been widely studied, we still don’t really know where they came from. Major gaps in the fossil record make it difficult to clearly understand their origin.

Dinosaurs Amazon
Amazonsaurus is so named because it was discovered in the interior of Brazil. Credit: Levi Martinez-Reza / Wikimedia Commons

The models suggest that the earliest dinosaurs emerged in a warm and arid environment, characterized by deserts and savannas. So far, no dinosaur fossils have been found in these specific regions of Africa and South America, likely due to the inaccessibility of the terrain or the limited research conducted there.

In their earliest stages, dinosaurs were significantly outnumbered by other prehistoric reptiles. These included pseudosuchians, ancestors of crocodiles that could grow up to 10 meters long, and pterosaurs, the first animals to develop powered flight (flapping their wings instead of gliding), which reached sizes comparable to modern fighter jets.

In contrast, primitive dinosaurs were much smaller, about the size of a chicken or a dog, and were bipedal. Most were omnivorous, adapting to their surroundings. The dominance of dinosaurs began around 201 million years ago, following volcanic eruptions that wiped out many of their reptilian competitors.

The study suggests that dinosaurs, along with other reptiles, originated in the low-latitude regions of Gondwana and later expanded southward and northward. Eventually, they reached Laurasia, a supercontinent that later split into Europe, Asia, and North America.

One highlight of the study is the possible link between silesaurids, reptiles traditionally considered relatives of dinosaurs, and ornithischians, a group of herbivorous dinosaurs that includes Triceratops and Stegosaurus. This connection could help bridge gaps in the evolutionary tree of dinosaurs.

Professor Philip Mannion, a co-author of the study, explained that early dinosaurs may have been well-adapted to warm, arid climates. Among the three main dinosaur groups, sauropods, like Diplodocus and Brontosaurus, continued to inhabit warm, low-latitude regions. However, theropods and ornithischians later developed the ability to generate their own body heat, enabling them to colonize colder regions, including the poles.


SOURCES

University College London

Joel A. Heath, Natalie Cooper, Paul Upchurch, Philip D. Mannion. Accounting for sampling heterogeneity suggests a low paleolatitude origin for dinosaurs. Current Biology, 2025; DOI: 10.1016/j.cub.2024.12.053


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