I was into dinosaurs when I was a kid, and now I'm teaching my kids about dinosaurs. In light how much our understanding of dinosaurs has drifted in 30 years, and after learning about how certain dinosaurs species are basically extrapolations based on, like, a single bone, I'm trying to get a sense of what we actually know about dinosaurs versus what is just being made up to fill in the gaps.

As an example of what I'm talking about, the wing span for quetzalcoatlus keeps being revised downward. They seem to have a few skeleton fragments, and then they extrapolated what the rest of the skeleton looked like based on other species which they assume to be similar. I find myself wondering if at some point they're just going to come out and say, "Yeah, this thing never flew at all, the assumption that it was just a bigger version of other azhdarchid species was completely wrong, sorry." Sometimes I read passages that suggest that pterodactyls may not have been fliers at all.

We've seen many similar revisions, such as the famous "T. Rex was a scavenger" and "all these dinosaurs had feathers". So if I had a pithy version of this "stupid question" it would be "What do we actually know about dinosaurs?"