You are exploring the marshlands of New Mexico, 300 million years ago. A sudden splash startles your side. You whirl around, just in time to notice an odd-looking reptile-like creature burst out of the water nearby and clamber onto dry land. The 10-pound amphibian crawls forward before lunging over to snatch a smaller reptile that has been hiding in the undergrowth of the swamp. Having caught its prey in between its teeth, the strange creature glances up to meet your gaze and lets out a guttural hiss, threatened by your presence.