Pisanosaurus VS. Patagotitan
110 MYA in Cretaceous Argentina, on an open floodplain, the seasonal rains have ended. The floodwaters have receded into river channels that now flow into a large, distant body of water. The ground remains saturated, and a huge diversity of plants are taking advantage of the ample sunshine and water availability, springing up across the expanse of land (Krause et al., 2020).
A young Pisanosaurus, arriving on this landscape from the Triassic period, is more familiar with volcanic activity, heavy rainfall, and ferns (Tucker & Benton, 1982). Nonetheless, the bounty of green prompts the animal to overcome hers initial discombobulation and begin to forage. Pisanosaurus is not alone. Many other small herbivores have ventured out onto the plain to feed, as much for the ready access to water that the stream channels provide as for the vegetation. This does not bother Pinsanosaurus, as she shares the ecosystems of her home with small rhynchosaurs and therapsids (Bonaparte, 1976), and has perceived no sign of any larger predators. Nevertheless, feeling exposed on the open floodplain, the small dinosaur begins to work her way towards the tree line upstream. There, deadfall and underbrush will provide ample hiding spots should the need arise. As cover and the promise of safety draws near, a disturbance in the trees ahead causes Pisanosaurus to pause, crouching low to the ground.
The canopy parts, and the shadow of what emerges is so monstrously large that it reaches out to shade Pisanosaurus where she quakes amongst the low plants. Adrenaline surges through Pisanosaurus’s veins and her heart begins to pound, trying to pump blood to the animal’s limbs and preparing her to fight or flee. Where to run though, when all that lies behind is an exposed plain, and danger in between the Pisanosaurus and any hope of concealment. The behemoth is now towering over Pisanosaurus, whose limbs and lungs feel paralyzed even as her heart works harder, and the world is swaying in her vision as pain spreads through her chest. The Pisanosaurus collapses to the ground.
The Patagotitan, weighing over 60 tons (Otero et al. 2021) and at a scale enormous beyond anything that Pisanosaurus would ever have encountered in the Triassic, wanders his way down to the water. He is completely unaware that his alarming emergence from the forest, in combination with a congenital heart defect, drove Pisanosaurus to an untimely and stress induced heart attack. Scavengers will eventually descend upon the carcass where she lies on the floodplain, or an unexpected rainfall will flood the land and see the body buried for future fossilization. It matters not to Patagotitan.