National Geographic : 1997 Dec
digit on its forelimb. Novas hadn't a clue what to call the thing-until he learned that a sim ilar creature named Mononykus had just been found in Mongolia. The resemblance was so close that he decided to name his specimen Patagonykus. Both creatures were from the late Cretaceous, long after Laurasia and Gondwana had drifted apart. How did continents sepa rated by thousands of miles of ocean end up harboring the same kind of dinosaurs? Did they both just happen to evolve the same weird anatomy? Or did land bridges or island chains occasionally link the continents even as they were spreading apart? "It's a complicated mess," says Sereno. As if to underscore his point, a gust of wind blows in off the river and erases his pictures in the dust. UNCOVERING PATAGONIA'S LOST WORLD Three-toed fossil tracks near El Chocbn mark the path of Limayichnusmajor, which lived when shifting continents transformed global environments. Pursuing traces of Patagonia's past, paleontologists leave deep imprints on our knowledge of dinosaurs and evolution. TILL, A MESSY, UNSOLVED MYSTERY holds far more promise than an unexamined assumption. No one knows yet where the splendid giants of Patagonia fit into the big picture of dinosaur evolution, but they can no longer be dismissed as bizarre no-counts that inhabited a dinosaurian back water. Rodolfo Coria, in fact, suspects the very opposite may be true. "I think the South American forms are the normal dinosaurs," he tells me, back in Plaza Huincul. "The oldest, most primitive predators come from Argentina. The same is true of the ornithischian dinosaurs and maybe even the sauropods. If you want to see bizarre dino saurs, go to North America and look at Tyran nosaurusor all those different ceratopsians." Coria admits there are still too few speci mens to make a firm case for his theory, but that may not last for long. Just a few months after my visit he unearthed three new giant predator specimens, at 90 million years old likely tormentors of the megasauropod Argen tinosaurus. A month later Ruben Martinez, a paleontologist at the National University of Patagonia in Comodoro Rivadavia, found a second, even more spectacular titanosaur skull farther south. Fernando Novas's team has re turned to the hills that produced Patagonykus and pulled out a frightening claw of a predator similar to JurassicPark's Velociraptorbut eight times its bulk. Even more fascinating is Unen lagia, a primitive, transitional birdlike creature from the same site-unable to fly but with flight foreshadowed in its forelimb. Those fos sils are destined to transform our understand ing of dinosaurs not only in Patagonia but all over the world as well. "That is the fun part of our work," says Coria, as he takes a sip of mate. "There is no last word. Maybe tomorrow a new hypothesis will open up, and another one will close." E[ For more on Patagoniandinosaursjoin our online forum at www.nationalgeographic.com.