You are in the floodplains of Europe, 154 million years ago.

The thick, humid air of the Late Jurassic Iberian floodplain was broken only by the sound of rhythmic snapping. Crouched behind the immense roots of a conifer, you watched a 9-meter-long Dacentrurus systematically strip bark from a tree.

It was vastly different from the more iconic Stegosaurus. Its front legs were surprisingly long, creating a less pronounced hunch, and the "plates" on its neck were almost vestigial, giving way to an menacing, elongated series of spikes running down its spine. As it moved, you saw the true weapon—not just two pairs, but a chaotic array of spikes near its tail, the dreaded thagomizer.