A Skeleton Dug Up in Tanzania in 1963 Sat in a London Drawer for 60 Years. It Turns Out to Be a Beast Known Only From South America, and It Makes the 'Oldest Dinosaurs' Up to 10 Million Years Younger.

A partial skeleton collected in Tanzania by a British expedition in 1963 and left largely unstudied in the Natural History Museum in London for more than six decades has turned out to be a new species of a genus previously known only from South America, and the identification is forcing paleontologists to rethink where and when the first dinosaurs appeared. The animal, named Dinodontosaurus isiyavamanda, was a dicynodont, a tusked, beaked, pig-to-cow-sized herbivore from the mammal lineage that dominated the land about 240 million years ago, before dinosaurs took over. The study, led by the University of Bristol, is published in the Journal of Vertebrate Paleontology.

The 1963 expedition brought back a large haul of synapsid fossils from what is now southern Tanzania, but only part of the collection was ever described. Hady George, a Ph.D. student in Bristol's School of Earth Sciences and lead author, examined one of the undescribed associated skeletons together with a fragmentary skull found more recently and concluded that both belong to Dinodontosaurus, a genus documented until now only in the Triassic rocks of Brazil and Argentina. Further anatomical work, including micro-CT scanning, showed the Tanzanian material is a distinct species. The name honors the land of the Wamanda people, who live in the region where the fossils were collected.

The consequence goes well beyond a new name on a museum label. The Tanzanian beds that produced the dicynodont are the same deposits that have yielded fossils long promoted as the oldest possible dinosaurs, or their closest relatives. Those rocks were dated by matching their fossil genera to rock sequences in South Africa thought to be Middle Triassic. Now that Dinodontosaurus is confirmed on both sides of the Atlantic, the Tanzanian beds correlate instead with South America, and new radiometric dates from South America put those early dinosaur-bearing sequences as much as 10 million years younger than the South African ones.

"Our discovery marks the first confirmed record of the genus Dinodontosaurus outside South America," George said. "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." In practical terms, Tanzania loses its claim to the earliest dinosaurs, and the search for where the group first evolved reopens.

The specimen's long wait is a story in itself. Nigel Larkin, now a visiting research fellow at the University of Reading, studied the skeleton for his master's thesis at University College London in 1994 and concluded then that it was a species new to science. "It took me nearly 30 years to start the process of writing it up for publication," he said. "I'm glad I waited, as the international team we put together, headed by George, has done an amazing job of fleshing out this story in much more detail and depth than I could have achieved on my own. And what's 30 years? It's the blink of an eye compared to the age of this prehistoric specimen."

Mike Day, curator of non-mammalian tetrapods at the Natural History Museum, said the fossil "has been in our care for over 60 years" and that its identification "goes to show how revisiting museum collections can change our understanding of the past just as much as finding new fossils in the field." Much of the Tanzanian Dinodontosaurus material, particularly the rest of the skeleton behind the skull, remains to be examined, and the team plans to compare it with the South American specimens and study how the animal moved and fed.