You are in the oceans of North Africa, 460 million years ago.

The water of the Ordovician sea was surprisingly warm, a vibrant turquoise shallow spanning as far as you could see. Below you, the seafloor was a bustling metropolis of ancient life—crinoids swayed like underwater trees, and tiny trilobites scurried over the limestone sediment.

Then, you saw it. Moving through the hazy sunlight wasn't a fish, but a long, straight cone, nearly five feet in length. It was an Orthoceras. It looked like a squid that had decided to live inside a perfectly straight, tapered shell rather than a curled one.

It was hovering silently, suspended in the water column using its inner air-filled chambers to control its buoyancy. You watched as its tentacles, arranged in a tight circle around its mouth, adjusted slightly, searching the water for plankton or unsuspecting prey. It was an apex predator, yet it carried itself with a slow, regal grace.

Suddenly, you made a sudden movement. The Orthoceras reacted with startling speed. It didn't just swim; it jetted. With a sharp expulsion of water from its mantle cavity, it darted backward, leaving behind a small cloud of ink to confuse you…