One of the most popular and well-known dinosaurs, Stegosaurus was a very unique looking dinosaur, with its large armored plates and distinctive tail spines. It lived during the Jurassic Period (around 150 million years ago) in the same time and place as Allosaurus. Broken tail spines and wound marks in Allosaurus bones suggest that these two may have done battle with each other.
Stegosaurus was first discovered during the so-called “Bone Wars” of the late 1800s, in which paleontologists Othniel Charles Marsh and Edward Drinker Cope each tried to outdo each other with new dinosaur fossil discoveries. It was originally named by Marsh, who believed its plates were arranged flat on its back like a turtle’s shell. This was later revised to a single row of plates, and then a double “mirrored” row. Eventually, remains were found that showed the currently accepted arrangement of alternating plates.
There were originally several different species of Stegosaurus described, but many of those have since been reassigned to other genera or consolidated into existing species. Stegosaurus belongs to the Stegosauridae family, in the subgroup Thyreophora, which also includes the Ankylosaurs.