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New African titanosaur discovered in cliff wall in Tanzania

Big news! Really big news. Paleontologists from Ohio University have unearthed a titanosaur from Tanzania, a new species of oversized dinosaur named Rukwatitan bisepultus, which had forelegs about 6 1/2 feet long and whose massive body probably weighed as much as several elephants.

The discovery described in the Journal of Vertebrate Paleontology adds some much-needed diversity to the titanosaur fossil record in Africa, where such enormous sauropods have been rare finds.

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The Rukwatitan bisepultus fossil, which included vertebrae, ribs, legs and pelvic bones, was spotted in the wall of a cliff in what's known as the Rukwa Rift Basin in southwestern Tanzania and dug out with the help of coal miners as well as professional excavators. The animal, a titanosaurian sauropod, died about 100 million years ago during the Cretaceous period.

It's not as big as other titanosaurian sauropods, including the formidable Dreadnoughtus schrani fossil from the South American region of Patagonia that was described last week. Dreadnoughtus measured 85 feet from head to tail and died somewhere between 84 million and 66 million years ago, just before all dinosaurs went extinct.

Such titanosaurs – big-bodied, plant-munching, long-necked animals whose members included some of the largest animals to ever walk the Earth – experienced a rise in diversity around the time that another group of sauropods known as the diplodocids were on the decline. (That group includes the somewhat famous Apatosaurus, which played a starring role in the animated children's film "The Land Before Time.")

So there should be a lot of titanosaur fossils lying around – scientists have found more than 30 in South America. But they've only found four in Africa – which is strange because Africa and South America were once part of the southern supercontinent known as Gondwana, and started to drift apart in earnest at the beginning of the Cretaceous.

"Whereas titanosaurians represent the most diverse and cosmopolitan clade of Cretaceous sauropod dinosaurs, they remain rare components of Cretaceous African faunas," the study authors wrote.

The new fossil, then, helps to fill in such gaping holes in the titanosaur family tree – and the relationships among various species. For example, there are some striking differences between the Rukwatitan bisepultus fossil and its relative Malawisaurus dixeyi in nearby Malawi. Those differences run across the body, from the structure of the humerus (the upper arm bone) to the "chevron" bones in the tail.

Rukwatitan is also very different from the known titanosaurs in northern Africa. This could mean that there was a land form – perhaps mountains or a river or desert  – that was keeping regional populations apart (and from interbreeding).

Follow @aminawrite for more science news from the 'lost world.'

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