Now for the classes. Dragon species and subspecies are categorized into different groups, known as classes. Dragons have various classes, just like they have various species.
Insectoid
Insectoid dragons have the appearance (or parts) of insects, arachnids, invertebrate, or any other arthropod. These dragons are usually characterized by having multiple eyes that make up one large eye, having exoskeletons aswell as skeletons, jointed appendages, and/or lacey insectlike wings.
Mammalian
Mammalian dragons have lots of fur covering most places, visible genitals, warm blood, and have the appearance (or parts) of mammals. Even though reptilian dragons can have fur, mammalian dragons have more fur than any other dragon.
Reptilian
Reptilian dragons are mostly covered in scales, have cold blood, and will molt and shed their skin as they grow larger. Reptilian dragons can grow fur, but they do not have as much as mammalian dragons do. These dragons are most common amongst stories and folklore.
Amphibious
Amphibious dragons, as their name suggests, spend part of their lives in the water and the other part on land. Their young are called nymphs, and when born may not have fully developed lungs, and must stay in the water until their lungs do develop fully. Amphibious dragons cannot spend their entire lives out of water, and if they try to, their skin will become dehydrated and they will die. Amphibious dragons may have very soft scales, or even no scales at all.
Aquatic
Aquatic dragons spend most of their lives in the water, and can have lungs, gills, or even both. Most aquatic dragons are incapable of flight, and use their "wings" as an extra pair of fins, which they use to glide through the water. They, like crocodiles and alligators, have the flap in the backs of their throats used for the same purpose. Their hands and/or feet are usually webbed, similar to a duck's feet or a fish's fins.
Hope this helped! If you have any questions, please message me or say so in the comments.
A part of my guide to making dragons o3o