A new prehistoric animal species from Tanzania dating back around 240 million years to the Triassic period has been described by an international team of researchers. Led by the University of Bristol, the new species, named Dinodontosaurus isiyavamanda, could help scientists refine the age of one of the world's most significant fossil sites, and reshape the timeline of early dinosaur evolution.
The study, published in the Journal of Vertebrate Palaeontology today [16 September], suggests that some of the earliest potential dinosaur fossils from Tanzania may be younger than previously thought.
More than 60 years ago, an extensive collection of synapsid fossils - mammal-lineage vertebrates that flourished before the rise of dinosaurs - was discovered during a British expedition in 1963 to what is now Tanzania. These fossils were housed at the Natural History Museum , London, but were only partly studied, leaving uncertainty over the identity of some of the fossils and what they could reveal about ecosystems approximately 240 million years ago.
By examining one of the undescribed associated skeletons belonging to a herbiovorous group of synapsids called dicynodonts, together with a more recently discovered fragmentary skull, the research team found that the fossils belong to the genus Dinodontosaurus. The discovery was unexpected, as Dinodontosaurus had previously been known only from South America.
Further anatomical study confirmed that the Tanzanian material represents a previously unknown species, which the researchers have named Dinodontosaurus isiyavamanda. The name is a reference to the land of the Wamanda people, who inhabit the region of Tanzania where the fossils were found. The discovery has important implications beyond the identification of a new species.
The Tanzanian rocks that yielded Dinodontosaurus isiyavamanda are the same geological deposits that have produced fossils thought to represent the oldest possible dinosaurs. These rocks were previously thought to share some fossil genera with rocks in South Africa, which were thought to be Middle Triassic.
As Dinodontosaurus is now known to exist in both Tanzania and South America, it provides a new link between rock sequences in both countries and indicates that they are of equivalent age.
New radiometric dates from South America suggest that these early dinosaur-bearing rock sequences are up to 10 million years younger than that of South Africa.
This adds further evidence that the Triassic rocks of Tanzania can no longer be regarded as preserving the oldest potential dinosaur fossils*, prompting a reassessment of when and where dinosaurs first evolved.
Hady George , PhD student in the School of Earth Sciences at the University of Bristol, and lead author, said: "Our discovery marks the first confirmed record of the genus Dinodontosaurus outside South America. The finding links the Tanzanian and South American fossil-bearing rocks, showing they are of equivalent age.
"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. Forthcoming research projects will examine the remaining fossil material and explore the biomechanics and ecology of Triassic dicynodonts."
Palaeontologist Nigel Larkin, Visiting Research Fellow in the School of Biological Sciences at the University of Reading, and a co-author, added: "I studied this dicynodont skeleton for my MSc thesis at University College London back in 1994 and judged it to be a species new to science, but it took me nearly 30 years to start the process of writing it up for publication. I'm glad I waited, as the international team we put together, headed by Hady 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.
"Techniques have improved vastly over the last 30 years too – we can do so much more with Micro CT scanning etc to examine such specimens than we ever could have imagined in the 1990s, and international collaboration is so much easier. And what's 30 years? It's the blink of an eye compared to the age of this prehistoric specimen."
Dr Mike Day , Curator of Non-Mammalian Tetrapods at the Natural History Museum, London, explained: "This fossil specimen from Tanzania has been in our care for over 60 years, and it's wonderful that its identity has now been brought to light. By revealing that Dinodontosaurus lived in South America and eastern Africa, it offers a glimpse of our planet 240 million years ago.
"It goes to show how revisiting museum collections can change our understanding of the past just as much as finding new fossils in the field, showing the importance of looking after these invaluable records of life on Earth."
The new discovery opens the door to further research. A large amount of the Tanzanian Dinodontosaurus material remains to be examined, particularly the postcranial skeleton.
Future work will investigate the anatomy of these remains and compare them with South American specimens. The researchers also plan to study the biomechanics of Dinodontosaurus and related dicynodonts to better understand how multiple large herbivorous species were able to coexist in Triassic ecosystems.
