A Strange Tusked Mammal Relative May Redraw the Timeline of the First Dinosaurs

This tusked creature was not a dinosaur but it could rewrite dinosaur history.

For more than 60 years, the broken skull and skeleton of a large animal from Tanzania’s Manda Beds sat in the collections of London’s Natural History Museum. In 1994, a graduate student studying the bones concluded they probably represented a species unknown to science.

But the fossil’s real importance would take decades to emerge.

Researchers have now finally identified the animal as a new species of Dinodontosaurus, a large herbivore with tusks that lived about 240 million years ago. Despite the name, it was not a dinosaur. Dinodontosaurus was a synapsid, part of the evolutionary branch that ultimately gave rise to mammals.

The surprise lies in both where and when it turned up. Until now, Dinodontosaurus was known only from South America. Its appearance in Tanzania creates a new link between African and South American fossil beds dating to the Middle and Late Triassic.

While not a dinosaur itself, this animal’s presence in Tanzania could shift one of the most important timelines in early dinosaur evolution. The same Tanzanian rock sequence has yielded the earliest proposed dinosaurs—or their close relatives.

If those rocks are closer in age to South American formations than previously thought, Tanzania’s famous “oldest dinosaur” candidates may not be as ancient as scientists once believed.

The Cousin from Tanzania

Both its name and appearance could be deceiving. For outsiders, Dinodontosaurus isiyavamanda would resemble a dinosaur.

“Imagine a huge pig with a turtle’s beak and tusks slightly shorter than those of a walrus,” Hady George, a paleontologist at the University of Bristol and the study’s lead author, told Discover Wildlife.

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The animal belonged to the dicynodonts (“two dog teeth”), a successful group of plant-eating synapsids—like Lystrosaurus or the giant Lisowicia.

The main specimen was collected during a British expedition to Tanzania’s Ruhuhu Valley in 1963. Nigel Larkin, now at the University of Reading, studied it for his master’s thesis in 1994 and recognized that it probably represented an undescribed species related to Dinodontosaurus. A second, fragmentary skull was recovered in 2012.

Modern CT scanning and 3D imaging allowed the new team to compare the bones in far greater detail with South American specimens. They found distinctive features of the palate, skull roof and jaw that justified naming a new species, D. isiyavamanda, after the land of the Wamanda people who live in the region where the fossils were found.

More important, however, was the genus itself.

“Our discovery marks the first confirmed record of the genus Dinodontosaurus outside South America,” George said in the University of Bristol announcement.

The Biological Link

Paleontologists cannot always date fossil-bearing rocks directly. In the Manda Beds, the problem is especially tricky because the fossil-rich layers have not been pinned down with the kind of precise radiometric dates available from some other Triassic sites. Researchers have therefore had to estimate their age by comparing the animals found there with fossils from better-dated rock sequences elsewhere.

Previously, Tanzania’s Manda Formation was correlated with older Middle Triassic rocks in South Africa. Shared animals seemed to support an Anisian age, roughly 247 to 242 million years ago.

But those correlations have weakened as paleontologists reassessed several supposed fossil matches. Dinodontosaurus points elsewhere.

The genus occurs in well-studied formations in Brazil and Argentina. Its appearance in Tanzania strengthens the case that these regions preserve animals from roughly the same interval. A 2016 radiometric study of Argentina’s Chañares Formation placed its major fossil-bearing interval around 236 to 234 million years ago, millions of years younger than some earlier estimates.

The researchers therefore argue that the mid-to-upper Lifua Member (Manda Beds) is more likely late Ladinian to Carnian in age, broadly between about 242 and 227 million years ago.

“The finding links the Tanzanian and South American fossil-bearing rocks, showing they are of equivalent age,” George said.

So… What Happened to the ‘Oldest Dinosaur’?

The Manda Beds also contain Nyasasaurus parringtoni—the oldest known dinosaur candidate.

When researchers formally described Nyasasaurus in 2013, they concluded that it was either a true dinosaur or its closest known relative. Under the former geological interpretation, Nyasasaurus could have lived around 247–242 million years ago—roughly 10 million years before the first widely accepted dinosaurs.

The old estimates made Nyasasaurus extraordinary. The new work curbs the enthusiasm.

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If the fossil-rich part of the Manda Beds is actually late Ladinian to Carnian in age, as the new Dinodontosaurus evidence suggests, then Nyasasaurus loses its title. Rather than predating the oldest undisputed dinosaurs, it may have lived much closer to the time when dinosaurs were already emerging elsewhere.

The authors caution that the exact layer that produced Nyasasaurus is uncertain, although it probably came from the mid-to-upper Lifua Member where most Manda fossils occur.

“This helps confirm that the oldest dinosaur candidates from Tanzania are probably no older than those from South America, refining the timeline of dinosaur origins,” George explained.

And Nyasasaurus is not the only fossil whose significance depends heavily on the age of these rocks.

The Manda Beds also produced Asilisaurus kongwe, a silesaurid first described in 2010. Silesaurids were close relatives of dinosaurs, although exactly where they belong remains debated: some analyses place them just outside Dinosauria, while others interpret them as early ornithischian dinosaurs. The Tanzanian Asilisaurus has was a strong sign that the dinosaur lineage was already diversifying unusually early in the Middle Triassic.

The new study argues that the relevant Manda rocks are more likely latest Ladinian to Carnian, bringing Nyasasaurus and Asilisaurus much closer in time to comparable dinosaur and dinosaur-relative faunas in South America.

Before Terrible Lizards

There is an irony in using Dinodontosaurus to rethink dinosaur origins. The animal belonged to a world in which dinosaurs were in their infancy.

Dicynodonts survived the end-Permian mass extinction and diversified into numerous herbivorous forms during the Triassic. The Tanzanian ecosystem alone contained several larger dicynodont species—like Tetragonias and Sangusaurus.

How so many bulky plant-eaters lived alongside one another remains an open question.

The new species may offer a clue. D. isiyavamanda had an unusual broad, bulbous ridge along its palate unlike those of other dicynodonts from the same rocks. The researchers suggest it may have processed food differently from its neighbors, allowing several large herbivores to divide up available resources.

For now, that remains a working hypothesis. The team plans further work on the animal’s biomechanics and the rest of the Tanzanian material.

Until then, the fossil has already accomplished something more immediate. A mammal relative collected more than half a century ago has become a key piece of evidence in the debate over when the first dinosaurs appeared.

And in the tangled early history of dinosaurs, the animal helping to reset the clock was not a dinosaur at all.

The study was published in the Journal of Vertebrate Paleontology.