The long snout shook back and forth as the Astrapotherium nipped off a tasty meal. It was a windy day, and it was this wind that covered the massive animal moving toward the feeding animal.
The grass parted silently in front of the creature, right before it leaped forward, a couple feet into the air and landed with a large boost of energy. The Astrapotherium turned its head quickly and snorted. Both creatures rushed off.
With strides covering many times that of his prey, the predator quickly ran up beside it and, with one swift move of his beak, struck the creature in the neck. The blow was directed right for the spinal cord, and that is right where it hit. The Astrapotherium dropped to the ground, paralyzed, before the predator, a gigantic, flightless bird tore him to digestible pieces.
The predator spoken of above was actually a group of flightless birds that are said to have conquered two whole continents as the top predator. According to the theory of evolution, even when the saber-toothed cats and wolves came onto the scene, these terror birds (otherwise knows as phorusrhacids), as they are known, still were the dominant predators for a long time.
With gigantic beaks, legs, bodies and acute senses, it comes as no surprise that phorusrhacids were so dangerous. Because these birds are flightless, this is usually the first thing discussed about them; well before any ideas on how they hunted.
The fact is flightless birds are still known today in the ostrich, penguin, etc. But, none of the birds living today had much of a build like the phorusrhacids. With the smallest known one being 3.3 feet tall and the largest at 10 feet, these birds could pack a punch to predator or prey.