Egg-laying Tissue in Dinosaur Bone (image) University of California - Berkeley Caption Cross-sections through the fossilized tibia or shinbone of a 120 million-year-old female Tenontosaurus skeleton, showing growth rings and medullary bone laid done in the marrow cavity just prior to egg laying. This individual died at the age of eight, shortly before she would have laid her eggs. Credit Sarah Werning/UC Berkeley & Andrew Lee/Ohio University; fossils courtesy of the Oklahoma Museum of Natural History Usage Restrictions None Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.