You are in the coastal swamps of North America, 280 million years ago.

The air in the early Permian swamp was thick, humid, and smelled intensely of wet ferns and sulfur. You were crouched near the edge of a slow-moving, shallow river, documenting the local flora, when the water’s surface broke just a few feet away.

It wasn't a shark, nor a large reptile. Emerging from the mud was a blue creature that looked like a living boomerang, perhaps two feet long from nose to tail. It was a Diploceraspis.

Its skull was wide and incredibly flat, with horn-like protrusions extending sideways and backward, resembling a B-2 bomber plane. The bizarre, aquatic amphibian didn't seem to notice you at first. It moved slowly, using its wide head to navigate the murky, shallow waters, browsing for small insects.

When you moved slightly to get a better look, its head abruptly snapped toward you, and it locked on with small, yet wide eyes. Fearing its sharp, needle-like teeth—typically used for scorpions and giant insects—you held perfectly still, as it lets out a wet, rattling hiss.