Life Before Dinosaurs Life Before Dinosaurs Dimetrodon Dimetrodon was a half mammal, half reptile with an unusual sail on its back. 5160352 Chasmatosaurus This early crocodile hunted down fish in the oceans and Lystrosaurus on land. 5894132 Dimetrodon 2 Dimetrodon was top predator in the early permian period. 5894133 Sea Scorpion Sea Scorpions like this were among the first creatures to crawl out onto land. 5894134 Scutosaurus Scutosaurus was a giant relative of the turtle with bony ridges on its back for protection. 5894147 Meganeura This giant dragonfly ruled the skies of the Carboniferous period feeding on smaller insects. 5894135 Trilobite (fossil) Trilobites were among the first creatures to swim the ancient oceans, they were mostly a food source for other creatures such as Anomalocaris. 5894148