Early Amphibian (Trimerorhachis insignis)

Fossilized early amphibian skullRecreation of an early amphibian
This animal was a precursor to the modern frog and was around in the early Permian period around 300 million years ago. It is widely believed the early amphibian had gills while it was alive. These creatures were found all over what is now Texas and the southern US. The fossil shown on the left was found in Baylor County, Texas.
Dinosaurs are not around yet, but the first mammals make their first appearance around this time.