13.There are plenty of animals that transition between bipedal and quadrupedal, but there are some animals that can only ever walk on two or four legs.
14.If he's quadrupedal, you want to make sure that what is absolute here from his performance is his two feet and the markers on the end of the arm extension.
15.Based on what you've seen and learned about the anatomy of dinosaurs, do you think this sort of track would have been made by a quadrupedal sauropod, or bipedal theropod?
16.But many other scientists think there was something between a bipedal ancestor and the pterosaurs – something that was arboreal, and quadrupedal that hasn't been found in the fossil record yet So the evolution of pterosaurs is still foggy.