Hiya! :>
I think on the first screenshot you posted, the chest is too curved - unnaturally so. Were you working with any specific animal in mind (bovine?), and were there any references available? I\'d recommend working with such as much as you can, since no matter how fantastical an animal may be, it still needs to have some basis in realistic anatomy and skeletal structure :) Speaking of which, the hind legs need at least three bones, counting from the hips - legs on quadrupeds, if modeled as a single bone, will make for some very awkward movement. Everyone needs knees :D
From the bulk you hint at in the first shot, I would think that the sides need to buldge out more in the second shot. It looks like a massive, heavy critter, so a thin chest and rib cavity is a bit odd.
It\'s a good beginning, but you can definitely take it further :)