A new species of dinosaur has emerged from the rocks in the western US state of Utah.

Researchers report in the journal PLoS One that the new dinosaur, buried by a collapsing sand dune, perhaps 185 million years ago, was probably a plant eater and an early relative of the giant animals later known as sauropods.

Named Seitaad ruessi, the species was 10 to 15 feet long and three to four feet high.

Its bones were found protruding from sandstone at the base of a cliff, directly below an ancient Anasazi cliff dwelling.

No humans were around at the time of the dinosaurs, but researchers said the bones could well have been visible when the early Indians lived there.