Seventy to ninety million years ago, generation after generation of dinosaur mothers returned to the same Patagonian floodplain to lay their eggs. Thousands of eggs litter the square-kilometer site near Auca Mahuida today, so many that researchers call the area Auca Mahuevo--huevo is Spanish for "egg." "It was impossible not to step on some of the eggshell fragments," says Lowell Dingus, a paleontologist at the American Museum of Natural History in New York. "It's rare to find an area not picked over by paleontologists, but there are areas in Patagonia that have not been explored." Tiptoeing through the eggshells, Dingus and his colleagues at AMNH and the Carmen Funes Museum in Argentina uncovered about 80 fossilized eggs and egg fragments containing embryos of sauropod dinosaurs. These are the first embryonic remains of sauropods, and they settle the controversy over whether the ponderous, long-necked, long-tailed dinosaurs produced live births. The eggs are about six inches in diameter. Some of the embryos are so well preserved that even their delicate skin, which looks remarkably like that of some modern lizards, has been fossilized, as these images show. Ancient streams may periodically have overflowed and buried the eggs in mud, which protected them from scavengers and erosion. Some embryos were 15 inches long and close to hatching. One specimen had 32 small, pencil-shaped teeth similar to those of plant-eating sauropods called titanosaurs, fossils of which have also been found in the area. If the embryos had grown to adult size, they might have reached 45 feet in length.