Artistic reconstruction of Mbiresaurus raathi (in the foreground) with the rest of the Zimbabwean animal assemblage in the background. It includes two rhynchosaurs (at front right), an aetosaur (at left), and a herrerasaurid dinosaur chasing a cynodont (at back right).

(Credits: Andrey Atuchin/Virginia Tech)

Roughly 230 million years ago, at the time when dinosaurs first came to be, the Mbiresaurus raathi pranced along the banks of an ancient river — modern-day Zimbabwe. While these 6-feet-tall sauropodomorphs (a relative of the towering sauropod) were definitely smaller than the nearly 100-foot-tall Brachiosaurus that made an appearance in Jurassic World, these long-necked and lithe creatures were hardly tiny.

These dinosaurs walked on two legs, had long tails, and weighed anywhere from 20 to 65 pounds. They also possessed the kind of sharp pointy teeth that were found in herbivorous or perhaps carnivorous species.

How do we know all this? Well, an almost fully intact skeleton, missing only some of the hand and portions of the skull, was unearthed in northern Zimbabwe in two digs — one in 2017 and another in 2019. And scientists have since managed to describe and name the animal.

“These are Africa’s oldest-known definitive dinosaurs, roughly equivalent in age to the oldest dinosaurs found anywhere in the world. The oldest known dinosaurs — from roughly 230 million years ago, the Carnian Stage of the Late Triassic period — are extremely rare and have been recovered from only a few places worldwide, mainly northern Argentina, southern Brazil, and India,” said Christopher Griffin, the lead author of the study.

The team, consisting of an international team of palaeontologists led by Virginia Tech, has not just uncovered what is Africa’s oldest dinosaur yet, but also shed new light on dinosaur evolution and migration, thereby filling some geographical gaps.

The M. raathi’s habitat was a rich ecosystem with more than just dinosaurs. The excavation revealed several protomammals called cynodonts, armoured crocodilians, beaked reptiles like the rhynchosaurs, and even evidence of an early meat-eating dinosaur.

And what’s intriguing about these finds is that this cluster of fossils is something that palaeontologists would expect to come across an ocean away — somewhere in South America.

But before there were separate continents, there existed one large supercontinent called Pangea. And the flora and fauna’s distribution across Pangea was divided based on the climate, with more temperate belts spanning higher latitudes and intense deserts across the lower tropics of the supercontinent.

The earliest dinosaurs were restricted to southern Pangea by these climatic bands and dispersed worldwide only later in their history. The research team hence developed a novel data method for testing this hypothesis of climatic dispersal barriers based on ancient geography and the dinosaurian family tree.

This is precisely why Griffin and his team purposefully targeted northern Zimbabwe as the country that fell along this same climate belt, bridging a geographic gap between southern Brazil and India during the Late Triassic Age.

The researchers propose that varied climate patterns held Triassic animals in place, and not physical boundaries like oceans. The closely-related dinosaurs found in South America, south-central Africa and India indicate that similar animals walked freely across this particular latitude band but not outside of it, likely because of climatic barriers like extreme heat or drought.

Meanwhile, M. raathi’s discovery in Zimbabwe has left a lot more room for further exploration of the fossil beds that it came from.

The findings of this study are detailed in Nature and can be accessed here.

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