First it was the badlands of the North American West. Then the deserts of Mongolia and western China. Now the arid plains of Argentine Patagonia, where layers of ancient rock are exposed by relentless winds and no plants obscure protruding bone or shell, are the latest El Dorado for paleontologists seeking dino remains. In just the last decade “we’ve found 12 new dinosaur [species],” says paleontologist Rodolfo Coria. Among the discoveries are the 120-foot-long Argentinosaurus, at 20,000 pounds the largest herbivore ever found, and Giganotosaurus, the carnivore that in 1993 dethroned Tyrannosaurus rex as the king of the meat eaters. The most spectacular find to date came in 1997, when scientists discovered an ancient nesting ground with hundreds of thousands of titanosaur eggs–many of them with fossilized embryos preserved inside. The eggs promise to reveal how the adults lived, how the embryos developed and how so many came to fill a mass grave.
The team that discovered Auca Mahuevo (fractured Spanish for “more eggs”) recently returned to the site with a NEWSWEEK reporter to find answers to those puzzles. Led by Coria, Lowell Dingus, a geologist at the American Museum of Natural History in New York, and Luis Chiappe, a curator at the L.A. museum, they set up their tent camp in a nearby ghost town. The abandoned hotel served as headquarters–it still has half its tin roof, and the door can be blocked with a table at night to keep out scavenging dogs and curious goats. Each member of the team had followed a different route to paleontology. Egg expert Gerald Grellet-Tinner–known as “the Bush Doctor” for his cocktail-mixing ability and habit of collecting goat skulls and meatball-size pollito spiders–is a former diamond broker and backgammon champion. Frankie Jackson, who studies abnormal eggshells, “ran away to join a dinosaur dig” in Montana after injuries ended her cowboy career. Marilyn Fox, who prepares fossils for study, used to create talking food for commercials.
The team spent their first day in the field this time searching for new eggs. They trekked from the exposed mud flat where they found the first eggs in 1997 toward cliffs a few miles away. As they walked, they followed the egg-containing layer like a paleontological yellow brick road, eventually reaching a spot on the cliff where the eggs were covered by only a few feet of stone. They quickly cleared the overlying stone from almost 400 square feet of the quarry, and in three days had excavated 80 eggs. All 80 lay in tight clusters or clutches, with no strays in between. “The clutches are two and three eggs deep,” says Dingus, “which would indicate that they were laid in depressions. If they were just piled up on level ground, they would have fallen.” Most clutches appear to be spaced an even 10 to 15 feet apart; it seems unlikely that natural depressions would result in such regular spacing. Instead, the dinosaurs may have dug nests, and spaced themselves out carefully to avoid crushing the next generation.
The next day the desert skies opened up and dumped a surprise rain on Auca Mahuevo. Three of Coria’s technicians rushed out to the egg quarry to throw a tarp over the partially exposed eggs, which would melt in the rain like spun sugar.
The eggshells themselves may provide as much information about the animals that laid them as the embryos do. Jackson, of Montana State University and the Museum of the Rockies in Bozeman, suspects that the abnormal eggshells she is collecting will reveal something about the lives of the mothers that laid them. In several egg clutches at Auca Mahuevo, Jackson identified “pathological eggs,” which have a double shell. That happens when the mothers are under stress and the eggs are retained for longer than usual inside the reproductive tract. Perhaps the nesting ground was overcrowded; congestion often causes double shells in crocodile eggs.
Two weeks into the expedition, Anwar Janoo of the American Museum was excavating around a large cluster of eggs. Taking extra care because he was unused to fieldwork, Janoo noticed two small bones where none should have been–outside the eggs, in the stone matrix that surrounds them. On closer inspection, the bones, from two pinkie-size limbs, were more fully calcified than those inside the eggs, so they may have belonged to a titanosaur hatchling. If so, the team will have a unique opportunity to study the early development of a dinosaur before it grew to maturity.
By the end of the month, the team had collected fossil bones from at least 20 embryos and more than a dozen patches of fossilized skin, and had mapped the distribution of eggs on the mud flat and at the quarry. The work at Auca Mahuevo will continue for years to come. But as this year’s season drew to a close, it was clear that the scientists were ready for the work to end, if just for a while. After four straight weeks of 12-hour days, in the hot sun and on the hard ground, it gets a lot tougher to get out of the sleeping bag in the morning. Early on, spare moments were spent walking the rock layers, prospecting for more fossils. Now team members are more likely to take a quick nap in the thin strip of shade beside their parked trucks. Back in camp, the scientists sit around a fire most nights, after a group meal that can be anything from salad and pasta to a chicken curry, courtesy of Janoo, who once worked in a Paris restaurant. They talk over the day’s finds and discuss plans for the morning. And as likely as not, they pass around a bottle of Argentine wine or a jug of cha jua jua, the semiofficial beverage of vertebrate paleontology, which seems to be made out of any liquor at hand and any available fruity liquid. But in the last days, talk has turned to flight plans and sample storage. While it’s hard to leave with so much still in the ground, Chiappe says he’s more than content with the success of the expedition. “You don’t want to get greedy,” he cautions. “Even for me, who loves being in the field, a month is enough. But after a couple of months at home, I’ll be back out, and loving it.”
