To offer a little pointless depth to the thread I have a couple thoughts. Asrodrig calls it a sail which is the correct term when referring to lizard anatomy. From what I can remember several reptiles have a sail appendage which they use to regulate their body temperature. Iguanas have a similar feature although it is below their jaws and not above their head. Being aboreal, this adaptation was what allowed them their paretial eye on the tops of their heads.
I could be wrong, but I believe the term 'crest' is used in GW to refer to the sail on the tops of their skinks' heads.
On the model, I send my compliments. It looks pretty balanced and I couldn't agree with you more about the wood. Painting it would have been a mistake for me, as I would have made it look worse. It definitely looks very natural but I can tell you that I could easily recognize it as Oxyotl if you told me that at the beginning of the game. Nice job!