New fossil sheds light on dino evolution

Researchers have revealed a new species of dinosaur they say sheds light on the evolution of sauropods, the group of massive herbivores that includes the brontosaurus, brachiosaurus, diplodocus and titanosaurs.

A team led by Eric Gorscak of Midwestern University, Illinois, US, describes the dino, Mnyamawamtuka moyowamkia, as an “exceptional” specimen of titanosaur from the mid-Cretaceous period, more than 100 million years ago. The fossil was found in the Rukwa Rift Basin of southwestern Tanzania.

Its unique bone structure, the researchers say, “adds evidence of a close relationship between the titanosaurs of southern Africa and South America, a link that was likely important in the evolution of Cretaceous ecosystems across southern continents”.

“Although titanosaurs became one of the most successful dinosaur groups before the infamous mass extinction capping the Age of Dinosaurs, their early evolutionary history remains obscure, and Mnyamawamtuka helps tell those beginnings, especially for their African side of the story,” says Gorscak.

He and co-author Patrick O’Connor of Ohio University, US, announced the findings in a study published in the journal PLOS ONE.

The specimen includes parts of “every major body region,” including teeth, vertebrae, ribs and limbs, making it one of the most complete specimens of titanosaur in the scientific literature, the authors say. According to the study, it has distinctive vertebral traits and “an unusually small sternal plate”, which helps distinguish it from other species in its group. 

Titanosaurs were the most widespread of the sauropods, evolving into numerous subspecies through the Late Cretaceous period (100 million to 66 million years ago), after other types of sauropods disappeared. Remains of the group, which had members up to 37 metres long, have been found on all seven continents.

The Mnyamawamtuka moyowamkia specimen was not nearly that large. 

“From foot to the top of the hips, it is about the height of an average person and probably weighed around a ton,” Gorscak told Cosmos in an email. “However, based on some of the bones, it was juvenile and certainly not fully grown, we’re just not sure how much larger it would have gotten!”

The specimen, the name of which comes from the Swahili words for “beast of the Mtuka” and “heart of the tail,” due to the shape of its tail vertebrae, is one of the most complete titanosaurs ever found in Africa.