This reminded me how rubbish I am at organic modelling, but on the up-side I have a much better understanding of T-Rex anatomy!
The difficulty with this 'mannequin' is that it isn't really possible to simplify the structure anything like as far as you can with a human, since the spine and tail need to be much more flexible if the model will eventually be pose-able. I reduced the number of vertebrae significantly but it'll still be a bugger to rig. Having bitten off more than I can chew again, I look forward to the 'chewing like crazy' bit to come...
NB: I added some articulation mechanisms as separate shapes to make it appear more like a physical mannequin, however these can be removed with no effect on the eventual rig. Also, while the teeth aren't strictly required, it looked silly without them!