Juvenile, Sam Noble Oklahoma Museum of Natural History. Photo by Matt Wedel
Our imaginations and everything we know bout dinosaurs has always told us that dinosaurs are enormous beasts.We know that Apatosaurus is one of the largest dinosaurs that traversed North America. However, it was also small at some point in its life. Small is subjective of course and we learn early on that we cannot always say something as simple as "it's large" or "that is small" when we are trying to describe or identify an animal or object in isolation. We keep saying that Apatosaurus is enormous, but we have yet to compare it to anything. For the sake of perspective, Apatosaurus is 22.8 m or 75 ft long. In comparing terms that means that Apatosaurus is approximately 1.5 school buses long. The juvenile shown above is significantly smaller, as we can tell by comparing it to the adult leg in the background. There are many specimens of Apatosaurus in museums, on display, and in ready-to-be-quarried quarries across the western regions of North America. These specimens are in various levels of completion, but because there are many that are significantly complete we have a very good idea of how large the animals were at different stages of life. That is why we can put adults and juveniles together, call them what they are, and not split them into different species.