A 73-million-year-old shoreline
The rocks in the Bowdoin Canyon area belong to the Wapiti Formation, a sequence of sandstones, mudstones, and coals laid down between 80 and 68 million years ago. During the Late Cretaceous Period, this region was a vast coastal floodplain, with rivers carrying sediment from the newly rising Rocky Mountains to the west. The fine-grained siltstones and sandstones of this ancient river system were perfect for preserving the delicate impressions of animal feet.
The trace fossils here reveal a surprising picture of pterosaur locomotion. Pterosaurs, the flying reptiles of the Mesozoic, were long thought to be clumsy on the ground. The trackways, identified by the ichnogenus Pteraichnus, show a very different story. These animals walked using all four limbs. The tracks consist of three-toed hand prints (manus) and four-toed foot prints (pes). The arrangement proves the pterosaurs used an erect, quadrupedal gait, planting their feet and the knuckles of their folded wings on the ground to move efficiently. One large isolated hand print measures 25.5 cm in length, suggesting a trackmaker with an estimated wingspan of 7.7 meters.
