Feature

The Earth Claw dinosaur rises again

Christina Scott

Wind and rain were scouring the fossils into dust. But a team of South African, Australian and American scientists got there in time. The result - a new species of dinosaur called Aardonyx, or Earth Claw.

Aardonyx life restoration by Matthew Bonnan

The new type of dinosaur, a long-necked vegetarian giant, was found almost by mistake on a Free State game farm outside Senekal.

For a start, fossils from the seven-metre-long Earth Claw, after surviving 195 million years, had been exposed and ''were in the process of being eaten away by erosion,'' said co-author and Pretoria geologist Johann Neveling from the Council for Geoscience.

In addition, ''I was reluctant to exacavate because getting to the site is a real pain,'' confessed lead author Adam Yates from the Bernard Price Institute for Palaeontological Research.

''We have to fill up the creek with stones and dirt to drive across. Every time it rains, this gets flushed away. And we seem to bring the rain,'' said the Australian-born dinosaur researcher, who is based at Wits University.

''At first I thought it was just another pile of common dinosaur bones,'' Yates added.

Then Boksburg-born student Marc Blackbeard came along, needing an honours level project, and began digging.

Adam Yates and Matthew Bonnan with Aardonyx Skeleton at BPI - photo by Bonnan

''On his very first dig, pretty much within the first few bones that got exposed, I realised that I'd been completely wrong about this site. It was something new and different, rare - unexpected, to say the least,'' Yates said.

''The rocks are full of fossil fragments. When the first skull bone came up, it was like 'wow, at last, something that's complete, that's promising.' There was no 'eureka!' moment but moments of excitement and the slowly mounting realisation that we had something special here.''

It took several years of painstaking digs through the bone bed for Blackbeard, now doing his Masters research, to piece together the final moments of the juvenile giant, a bulk browser who shoveled down his plant food.

''A lot happened to this dinosaur. It had been trampled after death,'' Blackbeard said. ''Maybe a flash flood washed the decomposing remains into a shallow channel. What was left was scavenged - there are marks on the bone that look like teethmarks and we found several large teeth from another carnivorous dinosaur nearby.''

''These fossils are part of our history,'' said Blackbeard. ''This dinosaur gives us insight into what happened on the African continent and insight into evolution. It's not just early man that evolved and moved out of Africa. Dinosaurs did too.''

 

Skeleton by Adam Yates

Aardonyx was an animal close to the common ancestor of the gigantic sauropod dinosaurs. Sauropods (known popularly as “the long-necked dinosaurs”) were the largest backboned animals to walk on land – with their long necks, tree-trunk legs, and whip-like tails some exceeded 100 feet in length! Aardonyx gives us a glimpse into what the first steps towards becoming a sauropod involved.

Although some of the skeleton has turned to dust, enough of the delicate bones were recovered to fill in missing gaps in our knowledge of the early Jurassic time, when Africa was a very different place, connected to all the land masses of the world.

Co-author Anusuya Chinsamy-Turan, a dinosaur bone specialist from the University of Cape Town, showed that Earth Claw died as a teenager. He or she would have grown even bigger if had survived.

''Not much is known about the early evolution of this type of dinosaur, a forerunner to the sauropods, which were the world's biggest-ever land-living animals. How did they come to be so big? When did they switch from two feet to four?'' asked Chinsamy-Turan, author of the book Dinosaurs of Africa.

"Aardonyx lies at the very heart of the transition from earlier two legged 'prosauropod' dinosaurs to the true four-legged sauropods. It is the closest known relative of the quadrupedal sauropods and their closest relatives, that wasn't itself a committed quadruped," said Yates.

According to Matthew Bonnan, a co-author in this study based at Western Illinois University, "the bones of the forearm are shaped like those of sauropods – this means that the forearm and hand could bear weight and that Aardonyx could drop onto all-fours as well as walk bipedally."

* The bones are currently at Wits university and will go on display in Pretoria's Transvaal Museum early in 2010. In the long run, a three-dimensional mounted skeleton is proposed for the planned dinosaur museum at the Golden Gate National Park in the Free State.

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