A baby duck-billed dinosaur inside its eggScientists may have solved the mystery of why the dinosaurs became extinct at the end of the Cretaceous period—while amphibians, birds, mammals and other reptiles all survived. They believe that baby dinosaurs took so long to hatch out and grow into adults that dinosaur populations failed to recover quickly enough after an asteroid crashed to Earth 66 million years ago. Because it took only a few weeks for the young of birds, mammals and other reptiles to develop, these animals had a significant advantage, being far better able than the dinosaurs to survive the long periods of drought or cold that followed the catastrophic impact.
Fossil dinosaur embryo (Photo: Jordi Payà)
Paleontologists at Florida State University and the University of Calgary, Canada, found it was possible to calculate how long it took for dinosaurs to hatch based on the “growth” rings found on the teeth of embryos. In the same way that a tree grows a new layer each year, teeth grow a tiny new layer of dentine each day. These layers, called Von Ebner lines, can be detected under a microscope.
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