The origins of dinosaurs, long a subject of fascination and scientific inquiry, may be far older and more elusive than previously thought. A new study, led by researchers from University College London (UCL), suggests that the remains of the earliest dinosaurs could still lie undiscovered in the Amazon, the Congo Basin, and other equatorial regions of South America and Africa. This groundbreaking research, published in Current Biology, challenges existing theories about the birthplace of dinosaurs and proposes an exciting new direction for future paleontological exploration.
Currently, the oldest dinosaur fossils known to science date back to around 230 million years ago, with key discoveries made in regions such as Brazil, Argentina, and Zimbabwe. These fossils, while revolutionary, suggest that dinosaurs had already been evolving for a significant period before these specimens emerged. This has led researchers to the compelling hypothesis that the earliest dinosaurs may have originated millions of years earlier than these existing fossils suggest, in a region that was part of the supercontinent Gondwana.
The Birth of a Hypothesis
The supercontinent Gondwana, which existed during the late Paleozoic and early Mesozoic eras, once included landmasses that are now part of South America, Africa, Antarctica, Australia, and India. The new study proposes that the earliest dinosaurs emerged in a hot, dry, low-latitude environment within Gondwana—an area that corresponds roughly to present-day Amazon, Congo Basin, and Sahara Desert. This region, which includes some of the most biodiverse and remote areas on Earth today, was likely quite different in the distant past but still a viable environment for the evolution of early dinosaurs.
Lead author Joel Heath, a Ph.D. student at UCL Earth Sciences and the Natural History Museum, London, noted, “Dinosaurs are well studied, but we still don’t really know where they came from. The fossil record has such large gaps that it can’t be taken at face value.” Heath’s comments underscore the uncertainty in the fossil record and highlight the importance of using computational models to fill in these gaps.
The researchers employed sophisticated modeling techniques to simulate the distribution of dinosaur fossils, using both known fossils and evolutionary trees of dinosaurs and their close reptilian relatives. The results suggest that the earliest dinosaurs likely originated in the equatorial regions of western Gondwana, areas that were characterized by desert-like and savanna environments—conditions hotter and drier than what was previously thought to be conducive to the early evolution of dinosaurs.
A Fossil Record Full of Gaps
One of the key challenges in understanding the origin of dinosaurs is the incomplete and fragmented nature of the fossil record. While many early dinosaur fossils have been discovered in places like Argentina and Zimbabwe, other regions that were once part of Gondwana—especially parts of South America and Africa—remain underexplored. This has led to the possibility that the earliest dinosaur fossils are still waiting to be uncovered in these regions. The study’s authors suggest that the lack of discoveries in these areas may be due to a combination of inaccessibility and insufficient research.
Despite the scarcity of fossils from certain regions, the researchers argue that the geological context of these areas, combined with new modeling techniques, supports the theory that early dinosaurs evolved in a different environment than previously thought. As Heath pointed out, “This might be because researchers haven’t stumbled across the right rocks yet, due to a mix of inaccessibility and a relative lack of research efforts in these areas.”
The Evolutionary Landscape: Dinosaurs vs. Reptile Cousins
During the period when dinosaurs first emerged, they were far outnumbered by their reptile cousins, which included groups like pseudosuchians—giant, crocodile-like creatures—and pterosaurs, the first vertebrates to evolve powered flight. These creatures were enormous, with some species growing as large as modern-day fighter jets.
In contrast, the earliest dinosaurs were relatively small, often no larger than a chicken or dog. These early dinosaurs were bipedal (walking on two legs) and are thought to have been omnivores, feeding on a variety of plant and animal matter. Though small and outmatched by their reptilian contemporaries, these early dinosaurs would eventually evolve into the dominant land animals on Earth, thanks in part to the extinction of many of their reptile relatives following volcanic events around 201 million years ago.
The Rise of Dinosaurs: A Hot and Arid Beginning
The new modeling study suggests that dinosaurs likely evolved in the low-latitude regions of Gondwana, which were characterized by hot and dry conditions. These early dinosaurs, adapted to such an environment, would eventually spread to other parts of the supercontinent, including southern Gondwana and the northern landmass Laurasia. Laurasia later split into the modern continents of Europe, Asia, and North America.
This model aligns with the geographical pattern of early dinosaur fossils. The earliest known dinosaur fossils have been found in southern Gondwana, while many of their relatives have been discovered in the northern supercontinent of Laurasia. The study suggests that western Gondwana, where these two fossil groups meet, might have been a central region for the early diversification of dinosaurs.
The study’s findings are also supported by the discovery of certain groups of dinosaurs that appear to have been well adapted to warm climates. For example, sauropods, the long-necked dinosaurs such as Diplodocus and Brontosaurus, are believed to have retained a preference for warmer, low-latitude climates throughout their existence.
Interestingly, the study also proposes that other groups of dinosaurs, such as the theropods (including Tyrannosaurus rex) and ornithischians (which includes herbivorous dinosaurs like Triceratops and Stegosaurus), developed the ability to generate their own body heat, a trait known as endothermy. This ability to regulate their internal temperature would have allowed them to thrive in cooler environments, such as polar regions, during the Jurassic period.
Filling in the Gaps: The Role of Silesaurids
One of the key findings of the study involves the silesaurids, a group of ancient reptiles that were once considered distant relatives of dinosaurs but not true dinosaurs themselves. Recent evolutionary studies, however, suggest that silesaurids might actually be the ancestors of one of the major dinosaur groups: the ornithischians.
Ornithischians, which include iconic plant-eating dinosaurs like Stegosaurus and Triceratops, are notably absent from the early fossil record of dinosaurs. The study’s model provides evidence that if silesaurids were indeed the ancestors of ornithischians, this would help explain the gap in the fossil record and provide a more complete picture of early dinosaur evolution.
Conclusion: Uncovering the Origins of Dinosaurs
The findings of this study open up exciting possibilities for future paleontological research. While we already know that dinosaurs began to thrive on Earth more than 230 million years ago, the true origins of these incredible creatures may lie in the still-undeveloped fossil beds of South America and Africa.
As researchers continue to explore remote areas of the Amazon, Congo Basin, and Sahara Desert, the hope is that new discoveries will shed light on the hot and arid environment where dinosaurs first emerged. These findings could ultimately reshape our understanding of dinosaur evolution, providing new insights into how these ancient creatures rose to become the dominant life forms on Earth.
While the study’s findings are still speculative, they offer a new framework for understanding the origins of dinosaurs, which have fascinated scientists and the public alike for centuries. By combining cutting-edge modeling techniques with fossil evidence and a re-examination of Gondwana’s geography, researchers are inching closer to solving the mystery of where and how the first dinosaurs walked the Earth.
Reference: Accounting for sampling heterogeneity suggests a low palaeolatitude origin for dinosaurs, Current Biology (2025). DOI: 10.1016/j.cub.2024.12.053. www.cell.com/current-biology/f … 0960-9822(24)01722-6