NEW YORK, NY.- They are some of the rarest of rare artifacts: fossil dinosaur eggs with the embryo still inside. And they are prized for what they can tell paleontologists about the adults that laid them. The exhibition The World’s Largest Dinosaurs features a scale model of a nest found at Auca Mahuevo, Argentina, one of the largest known dinosaur nesting sites in the world. While it isn’t always possible to figure out which dinosaur laid a particular egg, in this case, an embryo within an egg found at Auca Mahuevo site allowed scientists to identify these eggs as those of titanosaurs, a group of sauropods that included such species as Ampelosaurus and Saltasaurus. Herds of female titanosaurs are thought to have laid the thousands of eggs — 15 to 40 at a time — in shallow nests dug out with their huge feet in dry mud and sand over miles of ground at Auca Mahuevo. Titanosaurs are among the biggest sauropods, the group