Linnorms are the original dragons of Golarion, their positions supplanted by the arrival of the “true” dragons millennia ago. These original dragons are immense, scaled serpents, with two forward legs and rudimentary wings located directly behind the head. They are capable of magical flight and glide effortlessly among tangled pines and over twisted boulder-strewn terrain. While dangerous, linnorms lack the ultimate power of their younger cousins.
Linnorms make their homes in the wilderness of the kingdoms and apparently move easily across the rift between this plane and the First World of the fey. In addition, although black-hearted and treacherous beasts, they benefit from good relationships with fey creatures, such that a hunter might find unexpected obstacles when questing after a linnorm. The variety of linnorms is as yet undetermined, as the Ulfen people choose to identify them chiefly by where they were slain. Old sages speak of snow, slate, mire, and tagia linnorms, but whether these are separate species or merely the same type of creature in different habitats remains unknown.
Sources: Pathfinder Chronicles Campaign Setting