Expression

Some main human facial movements compared with those need for an anthro' character with a longer muzzle.

Some ideas on the muscular arrangement needed on an anthro' characters face to fulfil human expression and speech. Note that the zygomatic bone is one of the most important areas of the face, anchoring the large masseter of the jaw (for this herbivore) and the zygomaticus and levator labii muscles to control lift of the mouth for smiling. Ultimately the shorter the muzzle the finer these small expressive movements can be, he'll probably still end up curling his lips! I'd need to spend time on how this would look if fur where to cover the face.

Skull Ideas

The muscles of the jaw are rather large on animals both herbivore and carnivore.
This is important for the Zygometic Arch or cheek bone as both the Masseter and Temporal muscles influence its size and shape. Coloured are ideas on visual fields.

I want to make sure a human size brain could fit into something like a horse's skull but make sure that the mouth and nasal pathways were still usable. By enlarging the Occipital or base of the skull can accommodated this. The brow ridge may also help but it means losing the flat Frontal bone that give herbivores their distinctive sloping head shapes. 

Comparative Skull Proportions

Each skull is divided simply into 3 parts; red - the maxilla and the plains of the 'face'; green - the mandible; blue - the cranial vault; yellow - the Axis (1st cervical vertebra). Each represents to a rough scale the respective size of each skull element in a) human, b) canine and c) equine. Note the cranial vault does not directly represent respective brain size.

I've started with a thought on the sentient issues of anthro' characters. We would expect our characters to the be the singing, dancing types of the average human. So if we take the casual assumption that to have the same level of intelligence means having the same brain size of a human we soon need to adjust the proportions of the skull to accommodate this. Fig 2 indicates  a size of the cranial vault in blue of a human (a) that we'd need to apply to our animal skulls. How then do we balance this with the large jaw and jaw muscles of a herbivore or carnivore? What changes does a larger cranium make to that of the facial plains, particularly the Zygomatric (or cheek bones), the position of the eyes and visual field? We have a number of considerations to make and plenty of permutations dependent on species...

S-spine, C-spine

Comparison of axial skeletons of a human and canine, arrows note the number and directions of each spinal curve. (Not to scale).

We encounter an extreme number of issues when converting quadruped anatomy to that of a biped. Essentially it boils down to the evolution of each systems handling of its centre of mass. Human bipeds balance their weight over 2 legs, with the centre of mass moving between each stance leg, however a quadruped dog shifts its weight between fore and hind limbs during movement.

The spines of each system are therefore adapted to cope with each of these extremes. The S-shape spine of a biped has 4 notable curves, creating it's distinctive S shape. This maintains the centre of gravity when standing from the top of the spine down through the feet. These curves also facilitate weight transference with minimal effort. 

The C-shape spine of quadrupeds have only 3 notable curves that are near opposite to biped curves. The C-shape comes from the thoracic and lumbar regions curving upwards. I've drawn the canine above stood upright, this would bring it's centre of gravity in front of its feet, causing it to be unbalanced and fall forward. The curvature of its spine, particularly at the lumbar region would not support the weight of an upright torso, the curve is in the wrong direction.

This shows that we simply can't start our anthropomorphic characters by just standing a quadruped up on 2 feet. This and other anatomical issues make this a poor starting point, however, should we wish to maintain a degree of our chosen animals features in our anthropomorphic bipeds we can start adapting this anatomy into likely possibles. Lets explore these possibilities...