The Morrison formation, Colorado, 155 million ago. The Morrison formation sweeps through Colorado, Utah, Wyoming, Montana and the Dakotas. It was home to many plants and animals that made up a strange and exciting ecosystem with a confounding diversity of megafauna living side-by-side. Two of these animals were stegosaurus stenops and allosaurus fragilis. Many allosaurus specimens bare signs of healed injury and sometimes even pathology (injuries that likely resulted in death). This indicates that it lived a fast, active lifestyle and sometimes lacked caution to avoid such injuries. One specimen of allosaurus features a deep conical puncture wound to its pelvic "boot" or pubic bone (ouch) perfectly sized for a stegosaur tail spike.