Lindwurms are a sub-species of dragons that have no back legs, longer tails, and often larger wings than most species of dragons.
Lindwurms consist of mainly aquatic species, but do include airbourne variations and a few earthbound races. They are very rarely seen in rough terrains like rockpools and mountain slopes, though some species are specially adapted to those areas.
Lindwurms have a very flexible anatomy, due to the lack of hind legs. Without their bone stucture getting in the way, it leaves room for stronger, larger secondary wings, or in some cases fins. Like most dragons, they can have either feathered or bat wings.
(Incomplete, please add if you know of a lindwurm [add description and where you saw it])