Flying things that lived a long time ago

Inspired by an awesome XKCD comic, this is what I study using only the thousand most common English words. Well, it’s more of a description of the animals, but it’s still entertaining. I’ll work on it and get a better one later, but this is the start: 

I study flying animals that died a really long time ago. They are cold blooded animals and had some hair-like covering but lots of skin. They flew using a really long finger and skin that went from the end of the finger to their legs. They moved their arms up and down to push against the air and fly. These animals were the biggest flying animals ever, some as big as a bus, but others were small. Some had lots of teeth that they used to catch food, but others had no teeth and ate animals that live in water whole. I look at pictures of their inside hard body parts to guess how heavy they were. This can tell us if they would have been too heavy to fly, and how they could fly. Did they use their power to fly? Or just put their arms out and let the air push them? We can look at animals that live today to better understand animals that lived a long time ago.

If anyone wants to give it a go, try it out here!