Summary in Seconds: A new study suggests that dinosaurs may have first evolved in hot, low-latitude regions of ancient Gondwana – areas now part of the Amazon, Congo, and Sahara – much earlier than current fossils indicate. Using modeling to fill gaps in the fossil record, researchers propose that early dinosaurs were small, adaptable creatures that later rose to dominance after a mass extinction.
Scientists May Finally Have the Answer
The origins of dinosaurs – those iconic rulers of prehistoric Earth – have long intrigued scientists and fascinated the public. A new study, however, is challenging traditional assumptions and offering a compelling theory about where these ancient creatures first emerged.
While most of the world’s oldest dinosaur fossils have been unearthed in regions like Argentina, Brazil, and Zimbabwe, new evidence suggests their earliest ancestors may have come from equatorial zones of ancient Earth – territories that today include the Amazon rainforest, the Congo Basin, and the Sahara Desert.
Rethinking the Fossil Record
The oldest confirmed dinosaur fossils date back roughly 230 million years. Yet the diversity among these early specimens implies that dinosaurs had already been evolving long before the appearance of the fossils we have found. This discrepancy points to a hidden chapter in the evolutionary timeline – one that may now be partially revealed.
A study recently published in Current Biology employs advanced modeling techniques to address the incomplete nature of the fossil record. The researchers, led by Joel Heath of University College London, analyzed fossil data, evolutionary relationships, and ancient geographical patterns. Rather than assuming dinosaurs never lived in areas lacking fossils, they treated these zones as simply underexplored.
“Dinosaurs are well-studied, but we still do not really know where they came from. The fossil record has such large gaps that it cannot be taken at face value,” Heath noted.
The Birthplace of Dinosaurs: Equatorial Gondwana
According to the study, the earliest dinosaurs most likely originated in western low-latitude Gondwana1—a hot and arid region in the Late Triassic era2 that would have resembled modern deserts or savannas. This challenges the longstanding belief that dinosaurs evolved in more temperate environments.
Despite this new theory, no fossils of early dinosaurs have yet been discovered in present – day Amazonia or central Africa. Heath and his team argue this is due to both limited accessibility and a lack of paleontological research in these remote and often inhospitable regions.
Dinosaurs in the Shadow of Giants
In the Late Triassic period, dinosaurs were only a minor component of a diverse and reptile – dominated ecosystem. Other prehistoric reptiles, such as pseudosuchians3– the ancestors of modern crocodiles – shared the land. Some of these creatures reached lengths of up to 10 meters (33 feet).
Flying reptiles called pterosaurs also appeared during this time, becoming the first vertebrates capable of powered flight. Some species would eventually evolve to wingspans rivaling those of fighter jets.
In contrast to their later descendants like Diplodocus4 or Tyrannosaurus rex5, the earliest dinosaurs were relatively small – about the size of a chicken or a medium dog. They were bipedal, agile, and likely omnivorous. Their adaptability and small stature may have given them an evolutionary edge in the harsh landscapes of early Gondwana.
A Catastrophe that Changed Everything
For millions of years, dinosaurs remained overshadowed by other reptilian lineages. But around 201 million years ago, a series of catastrophic volcanic eruptions triggered the end-Triassic mass extinction6. This event wiped out many dominant reptile species and cleared the way for dinosaurs to rapidly expand and diversify.
As the environment changed, surviving dinosaurs migrated southward into areas like Argentina and Zimbabwe, and northward into Laurasia7– the supercontinent that later fragmented into present-day Europe, Asia, and North America.
Fossil records show that some of the dinosaurs’ closest relatives, including crocodile-like species, were present in northern Laurasia. This supports the theory that dinosaurs originated in equatorial Gondwana before spreading across the globe.
Solving an Evolutionary Puzzle
One of the most intriguing outcomes of the study involves the evolutionary lineage of dinosaurs. There is ongoing scientific debate about how different dinosaur groups evolved from their reptilian ancestors. To explore this, the research team tested multiple evolutionary models.
The most compelling model proposes that silesaurids8—a group of reptiles once considered distant relatives of dinosaurs – may in fact be direct ancestors of ornithischians9, one of the three major dinosaur clades. This group includes famous dinosaurs such as Stegosaurus10 and Triceratops11.
This reinterpretation could help solve a longstanding mystery: why ornithischians are missing from the earliest phases of the dinosaur fossil record. If they descended from silesaurids, it would bridge a critical gap in our understanding of dinosaur evolution.
Climate Adaptation and Dinosaur Success
The study also highlights how dinosaurs adapted to various climates over millions of years. Early dinosaurs may have thrived in hot, arid environments—a trait particularly evident in sauropods like Brontosaurus12 and Diplodocus, which appear to have remained in warmer regions throughout their existence.
In contrast, theropods13 (the group that includes T. rex and modern birds) and ornithischians seem to have evolved some degree of endothermy—the ability to regulate their own body temperature. This adaptation likely enabled them to colonize colder and more diverse habitats, including polar regions, especially during the Jurassic period14.
This flexibility may have been a key factor in their evolutionary success, allowing them to dominate terrestrial ecosystems for over 135 million years.
The Search Continues
Although the study offers a powerful new framework, the lack of direct fossil evidence from equatorial Gondwana remains a major gap. Future expeditions to the Amazon, the Congo, and the Sahara may one day uncover the missing links in dinosaur evolution.
If these regions do indeed contain the earliest dinosaurs, their fossils may still lie buried beneath dense rainforests or desert sands – waiting to rewrite the first chapter of dinosaur history.
As paleontology advances and new technologies allow researchers to peer further into Earth’s distant past, the story of dinosaur origins continues to unfold. This study reminds us that science is an ever-evolving narrative, and the greatest discoveries may still lie ahead.
References
Gajbhiye, Sanjana. “Where Did Dinosaurs Come From? Scientists Say They Figured It Out,” Earth.com, 1 January, 2025. https://www.pinterest.com/pin/367113807143208723/
Heath, Joel A. et. al., “Accounting for Sampling Heterogeneity Suggests a Low-peleolatitude origin of Dinosaurs.” Current Biology, Vol. 35, Issue 5. March 10, 2025, pp 941-953.
Notes
1. Gondwana: was a large landmass, sometimes referred to as a supercontinent. The remnants of Gondwana make up around two-thirds of today’s continental area, including South America, Africa, Antarctica, Australia, Zealandia, Arabia, and the Indian subcontinent
2. Late Triassic Era: The Late Triassic is the third and final epoch of the Triassic Period in the geologic time scale, spanning the time between 237 and 201.4 million years ago.
3. Pseudosuchians: the name means “false crocodiles”. This name has been used for almost a century, and traditionally meant only non-crocodilians, but when defined as a clade, pseudosuchia came to include the group “true crocodiles” as well.
4.Diplodocus: a very large, slender, quadrupedal herbivorous (four-legged plant eater) dinosaur with an extremely long neck and tail, small head, and massive limbs, from the Jurassic period.
5. Tyrannosaurus rex: a very large bipedal carnivorous dinosaur of the late Cretaceous period, with powerful jaws and small clawlike front legs.
6. End-Triassic mass extinction: The Triassic–Jurassic (Tr-J) extinction event (TJME), Often called the end-Triassic extinction, marks the boundary between the Triassic and Jurassic periods, 201.4 million years ago.
7. Laurasia: included most of the landmasses which make up today’s continents of the northern hemisphere, chiefly Laurentia (the name given to the North American craton), Europe, Scandinavia, western Russia, Siberia, Kazakhstan, and China. Laurasia’s name combines the names of Laurentia and Eurasia.
8. Silesauridae: are an extinct group of Triassic reptile-like animals closely related to dinosaurs, often considered their closest non-dinosaur relatives within the group Ornithodira.
9. Ornithischians: A major group of herbivorous dinosaurs characterized by a pelvis structure similar to that of birds.
10. Stegosaurs: A group of heavily built, herbivorous dinosaurs known for the distinctive plates and spikes along their backs and tails.
11. Triceratops: A large, plant-eating dinosaur with three facial horns and a bony frill, belonging to the ceratopsid family.
12. Brontosaurus: A long-necked, massive herbivorous dinosaur from the Late Jurassic, known for its whip-like tail.
13. Theropods: a group of bipedal, mostly carnivorous dinosaurs that includes species like Tyrannosaurus rex and the ancestors of modern birds.
14. Jurassic Period: A geologic time period, about 201 to 145 million years ago, during which many iconic dinosaurs, like sauropods and theropods, thrived.