Apatosaurus ajax - running babies, by Fabio Pastori
“This painting depicts a historic Morrison Formation site, Quarry 5 in Morrison, Colorado. Discovered by Arthur Lakes in the spring of 1877, this site is most significant because it produced the type of Stegosaurus armatus, Yale Peabody Museum specimen 1850. Sauropod remains have been documented at this site as well.
Recent investigations at Quarry 5 yielded trace fossils on the top of the beds that contain the body fossils, including tracks likely made by juvenile and adult Apatosaurus ajax. On a single ex situ boulder, juvenile sauropod trackways demonstrate two distinct footfall cadences – a near heel-toe hind track pattern, and a trackway that shows twice the amount of space (as compared to the aforementioned tracks) between footfalls in tracks the same size. This indicates that the two trackways represent distinct locomotion pattern: the closer footfalls a walking speed with the wider footfalls representing a low-speed ‘run.’
While the trackway of close footfalls does demonstrate relatively shallow, lunate manual tracks, the wider footfalls have no features representing manual tracks (either overstepped or not). This suggests the possibility that young Apatosaurus had the capability of moving short distances bipedally.
Patient work at Quarry 5 is ongoing - hampered by very hard, silicic sandstone.”
Matthew T. Mossbrucker. Director and Chief Curator | Morrison Natural History Museum