You are in the dry grasslands of South America, 2 million years ago.

The air in the South American savanna was humid and smelled of crushed grass and dry earth. You were hiking near a rocky bluff when a loud “Thwack!”, accompanied by the sound of grunting that broke the silence and stopped you in your tracks.

It wasn't rocks falling. Neither it was two freight trains colliding.

Through the haze of dust just thirty yards away, you saw them—three Doedicurus, each the size of a modern compact car, with two of them engaged in a slow-motion, high-stakes battle. These were the armored "tanks" of the Pleistocene, still roaming this secluded pocket of South America. Their carapaces, covered in thick, interlocking bony plates, made them look invincible.

One of them, a scarred male with a massive dome, was attempting to edge around its rival, which swung its tail—a heavy club tipped with sharp, conical spikes—against the challenger's armored side. The sound was a horrific clang that echoed across the valley. The third, a female, looks on the spectacle.

You watched, terrified and amazed, as the ground shook with every failed impact, as the two male armored herbivores continue to fight for the female.