Imagine for a second an armadillo. Its that small creature known for its thick, armor-like hide and its defense tactic of rolling itself into a ball. The biggest an armadillo can grow is the size of a small pig, and can weigh up to 60 kilograms (130lbs.). Now imagine one of those things the size of a Volkswagen Beetle. Glyptodon was this enormous placental mammal that lived up until 10,000 years ago, when they were possibly hunted to extinction. Weighing up to 2 tonnes, it was covered in a shell that was 2.5 centimeters thick, and was composed of incredibly durable bony plates. As with turtles, this shell protected it from predators. Its a good thing this creature couldnt roll itself into a ball like its modern descendants can. Imagine a Glyptodon with that capability: it feels threatened, rolls itself into a very large ball, and tries to escape from danger. In doing so, it starts rolling down a hill, and the forces of gravity and momentum cause it to gain speed. The devastation from such an impact wouldve leveled almost anything in its path.