With the discovery of a fossil embedded in a cliff wall in Africa, a previously unknown species has been added to the list of titanosaurs, giant dinosaurs that walked the earth around 100 million years ago, paleontologists say.
Researchers from Ohio State University found the species, dubbed Rukwatitan bisepultus, while doing fieldwork in southwest Tanzania.
Using excavating machines and help from local miners, the scientists unearthed ribs, limbs, pelvic bones and vertebrae of the massive creature from a group of dinosaurs known as titanosaur sauropods, among the largest and heaviest animals ever to walk the Earth.
The find is one of only a few titanosaur specimens ever found in Africa; most previous examples have come from other areas of the world, particularly South America.
While more than 30 titanosaur fossils have been unearthed in South America, Africa has yielded just four of the giant creatures.
CT scans made of the recovered bones from Tanzania showed the animal was distinct from any previous known dinosaurs of its type, said lead study author Eric Gorsack, an Ohio State doctoral candidate in biology.
"Using both traditional and new computational approaches, we were able to place the new species within the family tree of sauropod dinosaurs and determine both its uniqueness as a species and to delineate other species with which it is most closely related," he said.
Titanosaurian sauropods, which lived in the last era of the dinosaur age, were massive herbivorous dinosaurs with characteristic long necks.
Rukwatitan, while not the biggest of the type, likely weighed as much as several elephants, the researchers said.
Rukwatitan may have evolved as a separate species because of the particular environments in the Rukwa Rift Basin of Tanzania in which it was found, study co-author Patrick O'Connor, a professor of anatomy, said.
"There may have been certain environmental features, such as deserts, large waterways and/or mountain ranges, that would have limited the movement of animals and promoted the evolution of regionally distinct faunas," he said.
Around two-dozen bones of Rukwatitan were recovered after river drainage through the cliff face had first revealed them, the researchers said.
They help fill in the known evolutionary history of titanosaurs, which had been incomplete, especially outside of the South America region, one expert not involved in the study said.
Rukwatitan is significant in being "one of the very few Cretaceous-aged dinosaurs known from Africa south of the Sahara Desert," says Matthew Lamanna, a curator of vertebrate paleontology at the Carnegie Museum of Natural History in Pittsburgh.
"That part of the world is one of the biggest 'black holes' in our understanding of dinosaurs," he says.