In case you didn't know, some pterosaurs were enormous. Standing as tall as giraffes, and not too dissimilar (see here), means that their ability to fly has often been brought into question (see here for a negative, poppy article). Instead of wading straight into the debate, which gets pretty catty as the protagonists hail from different fields (from palaeontology to physics), we might start by supposing that they could fly (a paper in favour of this will be published soon, or so I hear....) as we would still have a pretty huge question to answer: how did they get up into the air?
For a longer discussion on this, see this excerpt from an upcoming book by palaeontologist Mark Witton (out next year by the looks of it). Put simply, the problem is as follows: pterosaurs appear to have not had strong enough legs to launch themselves into the air as birds do. This might not seem like a problem if you imagine the huge beasts diving off of cliffs and catching the air like a paraglider might, however, the larger pterosaurs are most abundant in flat, terrestrial environments, even preying on small dinosaurs. Without the use of powerful leg muscles, or cliffs to sail off, how on Earth did they launch themselves?
It turns out they very well might have used their incredibly strong flight muscles in their arms to do the job, using some acrobatics which to us might seem insane, yet are the same sort of movement used by some vampire bats. There are even rumours of a trackway showing this sort of movement. Trying to explain what this would look like seems like a lot of effort, especially considering that there is this excellent video:
I'd love to show the video side by side with another of a vampire bat taking off, as seeing the action for real is great for lessening incredulity, plus it shows how informed palaeontologists need to be about the extant zoological world. Instead, as finding a good video at short notice is not always easy, this short clip of a bat running on a treadmill can give you an idea of how bats achieve their previously unique launch.
Imagining the brobdingnagian pterosaurs launching themselves in this fashion would truly be a sight to behold, though when we remind ourselves that it is highly possible that pterosaurs were able to fly quite soon after hatching, then we get to imagine cute, little pterosaurs doing exactly the same. I'd pay to see it.