While pterosaurs aren’t actually dinosaurs, they are, of course, some of the more remarkable creatures of the Mesozoic. Usually, we picture huge pterosaurs gliding overhead.
So how did they get around when they weren’t in the air? This question has been a controversial one for some time, as there are several possibilities ranging from belly-dragging lizard-like locomotion to walking on their hind limbs with their spines horizontal like a bipedal dinosaur, to a more erect bipedal stance. However, in recent years, there’s been some evidence that at least some of them may have been quadrupedal.
It’s been suggested that being quadrupedal may have helped them generate the oomph to leap into flight – no small matter for the largest species of pterosaurs that weighed upwards of 150 pounds.
Here are a couple of articles, with illustrations.
http://pterosaur.net/terrestrial_locomotion.php
http://www.washingtonpost.com/national/health-science/where-have-all-the-big-birds-gone-a-look-at-a-past-giant–the-flying-reptile-pterosaurs/2014/04/14/35022d9e-beb3-11e3-bcec-b71ee10e9bc3_story.html