If I recall my 2E correctly, I believe the spinewyrm is a kind of spiny snake rather than a dragon... with the exception of the elemental drakes and the Dragon Kings, dragons of any sort tend to be pretty rare on Athas.
The spinewyrm is indeed of the Dragon type now. What's more, they stat it just like a true dragon, with twelve age categories. It does lack arms, legs, or wings, but it is a flying creature (IIRC) and quite intelligent also.
