National Geographic : 1998 Dec
To protect the fragile eggs, we coated both single speci mens and egg clusters in plaster that hardened into rigid jackets. Then we hauled them by truck from Auca Mahuevo to the Carmen Funes Museum in Plaza Huincul, about 130 miles away. Safely delivered, the egg clusters became the responsibility of museum preparator Sergio Saldivia (right), who painstakingly scraped away clay and silt. My work with fossils has taught me that without the right specimen preparation you can lose a lot of infor mation. In fact, I couldn't see the eight embryonic teeth preserved in one of the eggs we brought back to the United States (below, in a highlighted grouping above the point of a common pin) until Marilyn Fox, a prepara tor at Yale University's Peabody Museum of Natural History, had spent about 40 hours cleaning the fossil. The teeth, each less than a tenth of an inch long, provide the most persuasive evidence that these dinosaurs were probably titanosaurs, a far flung subgroup of sauropods. Most sauropods had wide, spatula-shaped teeth, but a handful had thin, pencil shaped teeth like those found at Auca Mahuevo. Among this group, titanosaurs stand out because they are the only sauropods found thus far in the Rio Colorado formation and they are the only ones known to have lived during the late Cretaceous, a geo logic period that spanned about 32 million years, including the time when these eggs were laid.