A new study suggests that the earliest dinosaurs originated in the supercontinent Gondwana, which comprised southern Morocco. These findings challenge previous assumptions, pointing to gaps in the fossil record and potentially rewriting the history of dinosaur evolution. Fossils of the very first dinosaurs may be buried deep under the Sahara Desert and Amazon rainforest. A new study reveals that the earliest dinosaurs likely emerged in the supercontinent Gondwana, which included the Sahara Desert, spanning North Africa, including southern Morocco. Published in the peer-reviewed journal Current Biology on January 23, the study changes our understanding of where and how dinosaurs first evolved. If unearthed, these fossils could radically rewrite the history of dinosaurs. Currently, the oldest known dinosaur fossils date back about 230 million years and were unearthed further south in places such as Brazil, Argentina, and Zimbabwe. «Dinosaurs are well-studied, but we still don't really know where they came from», said Joel Heath, a doctoral student in Earth sciences at University College London (UCL) and the study's lead author. «The fossil record has such large gaps that it can't be taken at face value». The study suggests that dinosaurs might have originated in hotter, drier environments than previously thought—regions made up of desert- and savannah-like areas, such as the Sahara Desert. «So far, no dinosaur fossils have been found in the regions of Africa and South America that once formed this part of Gondwana», Heath explained. «However, this might be because researchers haven't stumbled across the right rocks yet, due to a mix of inaccessibility and a lack of research efforts in these areas». Studying the evolutionary family trees of dinosaurs To reach their conclusions, the researchers analyzed dinosaur fossils, evolutionary family trees, and the geography of their time. They treated areas without fossil finds as missing information rather than assuming fossils never existed there. The study noted that early dinosaurs were far less common than their reptile relatives, such as the pseudosuchians (ancestors of crocodiles, some of which grew up to 10 meters long) and pterosaurs, the first animals to achieve powered flight. Pterosaurs could grow as large as fighter jets. Early dinosaurs, in contrast, were much smaller than the giants we associate with the group, like Diplodocus. They were roughly the size of chickens or dogs, walked on two legs, and were likely omnivores, eating both plants and meat. Dinosaurs began to dominate after massive volcanic eruptions 201 million years ago wiped out many of their reptile competitors. The researchers' modeling suggests that dinosaurs and other reptiles most likely originated in Gondwana at low latitudes before spreading later to other regions, including southern Gondwana and the northern supercontinent Laurasia, which eventually broke into Europe, Asia, and North America. This theory is supported by the discovery of early dinosaur fossils in southern Gondwana and their relatives' fossils in Laurasia. To address uncertainties about the relationships between ancient dinosaurs and their close relatives, the researchers tested three different evolutionary family trees. The results support the idea that dinosaurs originated in Gondwana, especially if silesaurids—traditionally considered dinosaur cousins—are recognized as ancestors of ornithischians. This group, which later included plant-eaters like Stegosaurus and Triceratops, is absent from the early fossil record. If silesaurids were their ancestors, it helps explain this gap. «Our results suggest early dinosaurs may have been well-adapted to hot and arid environments», said Professor Philip Mannion (UCL Earth Sciences), the study's senior author. He noted that sauropods—such as Brontosaurus and Diplodocus—retained a preference for warm climates, sticking to Earth's lower latitudes. «Evidence suggests the other two groups, theropods and ornithischians, may have developed the ability to generate their own body heat millions of years later during the Jurassic period, enabling them to thrive in colder regions, including the poles». It is worth noting that the earliest known dinosaurs include Eoraptor, Herrerasaurus, Coelophysis, and Eodromaeus.
