Scientists find ‘missing link’ between two-legged and four-legged dinos

November 11th, 2009 - 1:22 pm ICT by ANI  

London, November 11 (ANI): Scientists have discovered a fossil skeleton that appears to be the missing link between the earliest dinosaurs and the large plant-eating sauropods, which could help bridge an evolutionary gap between the two-legged common ancestors of dinosaurs and the four-legged giants, such as diplodocus.

According to a report by BBC News, the remarkably complete skeleton shows that the creature was bipedal but occasionally walked on all four legs.

“What we have is a big, short-footed, barrel-chested, long-necked, small-headed dinosaur,” explained Adam Yates, the scientist from the University of Witwatersrand in Johannesburg who led the research.

“The earliest ancestral dinosaur - the great grand-daddy of all dinosaurs - walked on two legs. This (one) is intermediate between those bipedal forms and the true gigantic sauropods,” he added.

The skeleton was discovered at a site in the Senekal district of South Africa.

Dr Yates explained that features of its feet and jaw, as well as its size, gave away its significance.

The dinosaur, Aardonyx celestae was a heavy, slow-moving animal.

“It had a lot of features we see on sauropods. Short, broad feet and a big, broad gut, so it was clearly a plant-eater that was bulk-feeding,” explained Dr Yates. “And the anatomy of the jaw shows it had a wide gape - to stuff more food in,” he said.

“It also had sauropod-like front feet,” he added.

“Its toe bones were very robust and solid, so its weight was being born on the inside of the foot. It was still bipedal, but it may have been going down on to all fours to browse,” he said.

The dinosaur dates from the early Jurassic period - about 200 million years ago.

“Although structurally it’s intermediate, it lived too late to be an actual ancestor, because true sauropods already existed then,” said Dr Yates. “So, at the time, it was a living fossil - the transition must have happened much earlier,” he added.

According to Dr Paul Barrett, a palaeontologist from the Natural History Museum in London, the discovery of Aardonyx helped “fill a marked gap in our knowledge of sauropod evolution”.

“It shows how a primarily two-legged animal could start to acquire the specific features necessary for a life spent on all fours,” he said.

“Evolution of this quadrapedal gait was key in allowing the late sauropods to adopt their enormous body sizes,” he added. (ANI)

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