Zircon Grains (IMAGE) University of Texas at Austin Caption These are examples of zircon grains used in a University of Texas at Austin study that showed the animal thought to be the oldest land-based air breather is younger than thought. Grain numbers and ages are indicated by the numbers. Credit University of Texas Jackson School of Geosciences Usage Restrictions credit License Licensed content 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.