Skeleton of the Proto-Dinosaur Marasuchus (IMAGE) University of Alberta Caption Skeleton of the proto-dinosaur Marasuchus -- a squirrel-sized carnivore that likely walked on all fours but ran on two legs. Credit Scott Persons Usage Restrictions With attribution to Scott Persons 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.