Those familiar with sauropod trackways (and who of us isn’t?) will know that these are often described as ‘wide gauge’ or ‘narrow gauge’ depending on the separation between the left and right sets of prints of a given animal. Obviously sauropods would have had trouble swinging their legs under the midline of the body when walking so they leave two parallel sets of tracks, though the gap between these can be low or high.
This is something I’ve read many times and certainly have no truck with the idea. But it’s hard to *see* such a possible difference on a single sauropod specimen when you have nothing else to compare it to. Thus once more we turn to the Carnegie and their pair of giants. Conveniently, these animals are of pretty similar gross dimensions so the comparison is easier to make and look at the difference and, wow. You can probably walk though the legs of Apatosaurus (upper) quite easily, but you’d have to turn sideways or squeeze a little to get though those of Diplodocus. It’s quite a difference for two animals that are fairly close relatives and of such similar size.