The earliest known dinosaur fossils date back to approximately 230 million years ago. Recent research suggests that even older fossils may lie in uncharted territories around the globe, and geographical barriers might be the reason why they haven’t been found yet.
An investigation done by the Natural History Museum in the UK and the University College London posits that there is a huge gap in fossil findings around the equator.
“So far, no dinosaur fossils have been found in the regions of Africa and South America that once formed this part of Gondwana,” says Joel Heath, lead author of the study.
“However, 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.”
Skeletons in the closet?
Scientists label the origins of dinosaurs as a great mystery, one of the reasons being that there is strong evidence that the very first fossils found were of dinosaurs formed from pre-evolving creatures. Laurasia, the northern landmass of Pangea, has uncovered remains of similarly aged dinosaurs (230 million years old), which heavily complicates the entire situation even further.
If the very first dinosaurs (we have found) formed from the already existing ones in Gondwana, where did they actually originate? The answer, according to paleontologists, lies in a huge gap around the equator that (presumably) contains no fossils or remains.
Carcass pieces have to be preserved quickly to halt disintegration, and even if perfectly preserved, fossils may still be lost to erosion or remain hidden deep underground. Paleontologists suspect that the earliest dinosaurs may have lived in regions where fossilization was rare—or in areas that are simply too remote to have been properly investigated.
The hunt for the missing evolutionary link
Heath, along with his peers, devised models that trace the evolution of dinosaurs backward in time. They studied fossil distribution, taxonomic data, and the prehistoric structure of Pangea. The model tackles the problem from a new angle—instead of assuming that gaps in the fossil record indicate an absence of dinosaurs, they treat these regions as areas of missing information.
The models corroborated the theory that dinosaurs first evolved in lower, hotter areas of Gondwana, specifically in regions that are now parts of Southern Africa and South America. These areas logically lie between where the oldest known dinosaur fossil skeletons were found, yet no additional pieces have ever been discovered.
“Our modeling suggests that the earliest dinosaurs might have originated in western, low-latitude Gondwana. This is a hotter and drier environment than previously thought, made up of desert- and savannah-like areas,” explains Heath.
One of the important leads comes from silesaurids, which are reptilian dinosaurs. Perhaps one of the biggest enigmas in dinosaur evolution is the early ornithischian know where dinosaurs can still be found.
According to Heath’s research, silesaurid dinosaurs might be a missing link that forms a potential base for the evolution of the Gondwanan primitive life at low latitudes.
“Our results suggest early dinosaurs may have been well adapted to hot and arid environments. Out of the three main dinosaur groups, one group, sauropods, which includes the Brontosaurus and the Diplodocus, seemed to retain their preference for a warm climate, keeping to Earth’s lower latitudes,” says senior author Philip Mannion.
