Dinosaur Embryos Show Detailed Fossilized Skin
For the first time, paleontologists have found fossilized embryos of dinosaurs so well preserved that their delicate skin has survived in mineralized form, providing a glimpse of reptilian scales in patterns bearing a family resemblance to the skin of modern-day lizards.
The embryonic dinosaur skin was one of several important discoveries made a year ago by a fossil-hunting expedition working in the parched northern Patagonian badlands of Argentina. Everywhere the paleontologists looked over an area more than a mile square they saw gray fossilized eggs, whole or in scatterings of shell, lying on the surface or buried to depths of 16 feet. They could hardly take a step without crushing egg shell fragments under foot.
The nesting site was found by scientists from the American Museum of Natural History in Manhattan and the Carmen Funes Museum in Neuquen, Argentina. They announced the discoveries yesterday in a news conference at the American Museum. More detailed descriptions appear in a report in this week's issue of the journal Nature and an article in the December issue of National Geographic magazine.
'Finding embryo bones is rare enough, but finding the tissue of embryos is truly spectacular,' said Dr. Luis M. Chiappe, a research associate at the American Museum and a leader of the expedition.
The paleontologists said the nesting site was about 70 million to 90 million years old, in the last epoch of the Age of Reptiles. A preliminary analysis by geologists indicates that the egg clusters were laid in the flood plain of ancient streams that sometimes overflowed, burying the unhatched eggs in layers of mud that protected them from scavengers and decay.
The eggs were about six inches in diameter, and each one would have had the volume of a dozen chicken eggs. Some of them, Dr. Chiappe said, were quite close to hatching. The baby dinosaurs would have started life a mere 15 inches long and grown to an adult size of up to 45 feet long.
One embryo had 32 tiny teeth that reminded paleontologists of sauropods, the giant plant-eating dinosaurs with long necks and tails, huge bodies and four elephant-shaped legs. A familiar sauropod is Apatosaurus, often called Brontosaurus. But Dr. Chiappe said the teeth and scale patterns of the Patagonian embryos suggested that they were related to a different type of sauropods known as titanosaurs.
Dr. Rodolfo A. Coria, director of the Carmen Funes Museum, said the embryo discoveries had opened 'large doors that had been closed for years' and should yield important insights into the physiology and growth rates of sauropod dinosaurs.
The discoveries, Dr. Chiappe said, were also remarkable because they were the first dinosaur embryos found in the Southern Hemisphere and the first known embryos of sauropods. Paleontologists look forward to finding and studying more southern specimens to broaden their understanding of dinosaur evolution, which until now has been based almost exclusively on fossils from the Northern Hemisphere. And the fossil hunting has been especially rewarding in recent years in the relatively unexplored Patagonia.