Phylogenetic Tree (image) National Science Foundation Share Print E-Mail Caption This is a phylogenetic tree showing mammal backbone evolution: Edaphosaurus, Thrinaxodon, today's mouse. Credit Harvard University Museum of Comparative Zoology. Usage Restrictions None 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.