It lived on Earth
Stegosaurus lived during the late Jurassic in North America, about 150 million years ago. Only large theropods could have hunted Stegosaurus. Large theropods that lived alongside Stegosaurus include Allosaurus, Saurophaganax, Torvosaurus, and potentially Ceratosaurus (it might have been too small to hunt a Stegosaurus).
how big they were and how they lived
It was no more muddy or gross when Stegosaurus lived than it is today. In fact, Stegosaurus lived in a semi-arid plain with distinct wet and dry seasons. Except during the rainy season, there probably wasn't very much mud where Stegosaurus lived. However, there probably was a fair amount of dinosaur dung.
Stegosaurus lived between 155 and 150 million years ago. That was during the Upper Jurassic epoch.
We know very little about Stegosaurus behavior. What we do know is that they were herbivores, and that they lived in multi-aged herds with juveniles and adults. This suggests that Stegosaurus raised their offspring.
Like all dinosaurs, Stegosaurus lived in the Mesozoic era. It lived 150 million years ago. That was during the Jurassic period, the second period of the Mesozoic.
There is no animal called the sitta osaurus. There is however, a stegosaurus. A stegosaurus was a herbivore that lived during the Jurassic and Cretaceous periods.
Albertosaurus lived between 71 and 68 million years ago. Stegosaurus lived between 155 and 150 million years ago, meaning that they died out 79 million years before Albertosaurus existed. If they had lived at the same time and in the same place, though, Albertosaurus would have hunted Stegosaurus.
millions of years ago
Stegosaurus probably lived throughout most of the contiguous USA. However, its fossils are only known from Colorado, Wyoming, and Utah.
Stegosaurus existed from about 155 to 150 million years ago. That was during the Kimmeridgian and Tithonian stages of the Jurassic period.