Ancient Otter Tooth Found in Mexico Suggests Mammals Migrated Across America (video) University at Buffalo Share Print E-Mail Loading video... Caption An ancient otter tooth recently discovered in Mexico suggests certain mammals migrated across America during the Miocene geologic epoch, roughly 23 million to 5.3 million years ago. Credit University at Buffalo. Usage Restrictions Embargoed until 8:15 p.m. (EST) Tuesday, June 13. Share Print E-Mail 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.