Studying dinosaur eggs is a lot like a big, frustrating Easter egg hunt: The eggs are rare, fragile—rainwater is acidic enough to dissolve some egg fossils—and it can be difficult to identify which dinosaur species they belong to.
But every now and then, scientists' persistence pays off. A recently discovered clutch of 150-million-year-old fossil eggs is being billed as an important missing link in the evolution of dinosaur eggs.
The find from the Late Jurassic period, described in a paper published May 30 in the journal Scientific Reports, gives scientists a picture of early dinosaur eggs and embryos from a group called theropods, which include Tyrannosaurus rexand modern birds.
"Most of the time, you find eggs without the embryos, or the embryos without the eggs," said said Ricardo Araújo, a vertebrate paleontologist at Southern Methodist University in Dallas, Texas, and lead author of the new study.
This is the first real picture of what early eggs in theropods might have looked like, said Robert Reisz, a vertebrate paleontologist at the University of Toronto, who was not involved in the study.
The find will enable researchers to begin to address questions like which aspects of theropod eggshells came from their ancestors, and which ones evolved independently. (Learn more about dinosaur eggs.)
Gaps in the Record
Much of the fossilIzed egg material that scientists have found up till now belongs to the theropods, and dates to the Cretaceous period—about 80 million years ago. There are older dinosaur eggs from the Early Jurassic, or about 190 million years ago, but they belong to a sister group of dinosaurs called the sauropods. (Learn about the life of sauropods.)
