A is for Archaeopteryx
I love the shape of this word. It's exotic and fantastical and ungainly all at the same time - a little like the creature itself.
The word derives from the Greek archaeo (ancient) and pterux (wing). So, "Ancient Wing".
What's really cool about it, of course, is that archaeopteryx is an illustration of the forces of evolution in progress. It's a miraculous snapshot in time of a species part-way through the process of changing from dinosaur ancestor to modern avian descendent. It had a bony tail, teeth and feathers. And claws on its wings.
Once thought to be the "first bird" there are now older fossils that make that claim. Still, how fine it would have been to see an archaeopteryx in flight ...