Fossil shows dinosaur caught in collapsing sand dune

Researchers have discovered a nearly complete fossil of a dinosaur which appears to have been caught in a collapsing sand dune.

The Seitaad ruessi fossil, described in the journal PLoS One, is a relative of the long-necked sauropods that were once Earth's biggest animals.

S. ruessi, found in what is now Utah, could have walked on all four legs, or risen up to walk on just two.

It is from the Early Jurassic period, between 175 and 200 million years ago.

At that time, all of Earth's continents were still joined in the super-continent Pangaea, and sauropodomorphs like S. ruessi have been found in South America and Africa.

Unlike the sauropods to which they are related, S. ruessi was relatively small, about a metre tall and 3.5-4m long with its lengthy neck and tail, weighing in at between 70 and 90kg.

Plant life

Much of the fossil, first discovered by a local artist in 2004, was perfectly preserved in sandstone. However, it is missing its head, neck and tail.

Joseph Sertich of the University of Utah and Mark Loewen from the Utah Museum of Natural History have since then worked to free S. ruessi from its sandy grave - in an arid part of the US that, 185 million years ago, formed part of a huge desert.

"Although Seitaad was preserved in a sand dune, this ancient desert must have included wetter areas with enough plants to support these smaller dinosaurs and other animals," said Mr Sertich.

"Just like in deserts today, life would have been difficult in Utah's ancient 'sand sea.'"