Fossil discoveries suggest the earliest dinosaurs laid soft-shelled eggs
Eggs from the earliest dinosaurs were more like leathery turtle eggs than rigid bird eggs. Studies of fossilized embryos from two kinds of dinosaurs, one from early in dinosaur history and the other living about 150 million years later, reveal the eggs were enclosed by soft shells, paleontologists report online June 17 in Nature. The discovery marks the first time scientists have identified soft-shelled dinosaur eggs. Further analyses of these and other dinosaur eggs suggest that hard eggshells evolved independently for each of the three main dinosaur lineages: the long-necked sauropods, plant-eating ornithischians and fierce theropods. Until now, paleontologists thought that all dinosaurs had hard, mineralized eggshells. But scientists couldn’t explain why eggs from the earliest dinosaurs haven’t appeared in the fossil record or why microstructures within eggshells are so different for each of the main dinosaur lineages. “This new hypothesis provides an answer to these problems,” says Stephen Brusatte, a paleontologist at the...