You are in the shallow lagoons of Europe, 240 million years ago.

You were exploring the shallow, sun-dappled lagoons of the Triassic Tethys Sea when you spotted a truly bizarre sight. Resting on the sandy floor, a creature resembling a "reptilian walrus" was methodically working through a bed of shellfish. It was a Placodus, about two meters long, with a heavy, barrel-like body armored with bony plates along its back.

It moved slowly, using its webbed feet and a long, thick tail to navigate the shallow water. You watched as it deployed its most striking feature: front teeth that protruded straight forward like a picket fence, which it used to tear brachiopods and mollusks from the rocks.

After loosening the prey, the beast moved the shells to the back of its jaw, where massive, flat, pavement-like plates effortlessly crushed the shells with a sickening crunch. It seemed completely indifferent to your presence, focused entirely on its slow, powerful feast...