Not sure yet, as this guy was generated via a series of quick thumbnails, and if I continue to develop him he may lose/gain some features. But I imagine he could evolve from a rhinoceros, or a monoceros/unicorn. The various spikes and spines are majorly for defense purposes against the large dragons that roam the skies and other as of yet undeveloped terrestrial predators.
The small tusks jutting from his cheeks could be for battles over male dominance. I can imagine these guys whacking each other with their heads like giraffes, and the blunt protruding tusks would add extra damage to those swings. The tail is short but it can still whack away any predator that attempts to jump up on its hindquarters.