In addition to the discovery of Mbiresaurus raathi, Africa’s oldest known dinosaur species, Yale University paleontologist Christopher Griffin and his colleagues offer a new theory on early dinosaur migrations, including the when and where.
Africa, like all the continents that exist today, was once part of the supercontinent called Pangaea.
The climate across Pangaea is thought to have been divided into strong humid and arid latitudinal belts, with more temperate belts spanning higher latitudes and intense deserts across the lower tropics of Pangaea.
Scientists previously believed that these climate belts influenced and constrained animal distribution across Pangaea.
“Because dinosaurs initially dispersed under this climatic pattern, the early dispersal of dinosaurs should therefore have been controlled by latitude,” Dr. Griffin said.
“The oldest dinosaurs are known from roughly the same ancient latitudes along the southern temperate climate belt what was at the time, approximately 50 degrees south.”
Dr. Griffin and co-authors purposefully targeted northern Zimbabwe as the country fell along this same climate belt, bridging a geographic gap between southern Brazil and India during the Late Triassic epoch.
More so, the earliest dinosaurs were restricted by climatic bands to southern Pangaea, and only later in their history dispersed worldwide.
To bolster this claim, the paleontologists developed a novel data method to test this hypothesis of climatic dispersal barriers based on ancient geography and the dinosaurian family tree.
The breakdown of these barriers, and a wave of northward dispersal, coincided with a period of intense worldwide humidity, or the Carnian Pluvial Event.
After this, barriers returned, mooring the now-worldwide dinosaurs in their distinct provinces across Pangaea for the remainder of the Triassic period.
“This two-pronged approach combines hypothesis-driven predictive fieldwork with statistical methods to independently support the hypothesis that the earliest dinosaurs were restricted by climate to just a few areas of the globe,” Dr. Griffin said.
“The early history of dinosaurs was a critical group for this kind of problem,” said Virginia Tech researcher Brenen Wynd.
“Not only do we have a multitude of physical data from fossils, but also geochemical data that previously gave a really good idea of when major deserts were present.”
“This is the first time where those geochemical and fossil data have been supported using only evolutionary history and the relationships between different dinosaur species, which is very exciting.”
The study was published in the journal Nature.
C.T. Griffin et al. Africa’s oldest dinosaurs reveal early suppression of dinosaur distribution. Nature, published online August 31, 2022; doi: 10.1038/s41586-022-05133-x