WALK LIKE A DINOSAUR: These dinosaur footprints were left in a coastal mudflat in Yemen 150 million years ago.
Nancy Stevens

Dinosaur tracks recently discovered on the Arabian Peninsula are not only the first of their kind in the region, but they also reveal more about the herding behavior of the prehistoric beasts.

The footprints, left by a group of 11 plant-eaters that walked on all fours, along with a lone dino that stood on its hind legs, were found on a coastal mudflat in Yemen.

The footprints left by the herding herbivores varied in size, implying a roving group of adults and children. "Smaller individuals had shorter stride lengths, and took more steps to keep up with the larger individuals," says Nancy Stevens, an assistant professor of paleontology at Ohio University in Athens, and a co-author of the paper describing the evidence published online by PLoS ONE.

Researchers identified the quadrupedal roamers as sauropods, which had long necks and tails attached to a beefy, elephantlike body. The adults in the sauropod group likely rose 10 to 13 feet (three to four meters) in height making them about as tall as, but probably longer than a bus. The tracks, which run alongside an ancient waterway that has since dried up, imply that the wandering herd may have been searching for food. "This mudflat would have been like a highway for them, with little tree cover," says lead author Anne Schulp, a paleontologist at the University of Maastricht in the Netherlands.

The second set of tracks, which head in the opposite direction, belonged to an upright-standing dinosaur called an ornithopod. The scientists say it is unlikely the sauropods were in danger or felt threatened if they crossed paths with the other dino, because it was also a plant eater. Nevertheless, Schulp says he would not be surprised to find remains of large carnivores nearby, because they typically lurked wherever potential prey hung out.

Some fossils of dinosaurs related to the mudflat walkers have been found in Africa and date back to the same epoch of approximately 150 million years ago. This shows that these creatures co-existed in eastern Africa and on what later became the Arabian Peninsula, a large land mass that later separated from Africa, with the Red Sea forming in between.

Given the many rock outcroppings in the region, as well as the mudflats that preserved the plodding dinosaurs so well, Schulp believes that a wealth of information remains untapped in the Arabian Peninsula: "We have just scratched the surface," he says. "We're pretty sure there's a lot more to discover out there."