Why bother telling you about philtrums? Well, the answer is one of observation. Whenever you take a look at another human being's face, you inevitably (yet perhaps unconsciously) take in their philtrum as well. Without it, the face would lack some definition. It wouldn't communicate as well. Hence, when I was originally considering how to construct a maw at the front of a rhino, I examined a number of photographs of lips - both human and animal. In the end, I thought human lips would look more chaotic somehow. Also, they don't tend to protrude forward as much from the other parts of the face (eyes, forehead, etc.) as, for instance, a dog's mouth does. This meant that I could keep the approximate profile of the rhino intact. Significantly (and the deciding factor to use human-styled lips) was the observation of the philtrum. It was a feature that I felt I could pull off well, given a liberal amount of greenstuff. Moreover, it is also the feature that I think sets this rhino apart from others. It looks like it could have once been human, or is perhaps emulating a human mouth. Hence, I could also use this rhino as a possessed vehicle without stretching anybodies imagination (although I never have!).
Construction.
The first step was to cut out most of the lower half of the frontal armour of the rhino with a sharp hobby knife. I also dug in to the lower "floor" of the rhino where it connected to the frontal armour to create a more oval-shaped hole at the front. This formed the basis for the mouth's opening.
I then assembled the "teeth" of the maw. These were cut from the swords of some rather ancient warhammer fantasy battle skeleton sprues that I had discovered decaying in the nether regions of my bits box. A total of nine were used in the end. I did wonder whether to use scythes (thereby creating warped teeth), but I figured some pointy straight teeth would be better when combined with a decayed paint scheme. (An alternative would be to take apart a plastic hair comb and use the comb's teeth as proper teeth?). The teeth were then glued in to position - alternating between downward and upward pointing ones. They were also orientated such that they were pointing slightly outward from the body - the remains of the frontal armour helped with this as its angle is almost spot on already.
Then, I made up a whole load of greenstuff / milliput. It was pushed in an oval shape around the hole created in the front armour and such that it didn't connect with the pointed end of the teeth. Next, this shape was slowly pushed, with finger and thumbs, in to a more mouth looking shape. This, of course, included creating a convincing looking philtrum and lip regions. The lips were scored with some straight lines to give the impression of a different texture compared to the upper lip / moustache area. The result looks a bit like a snarl!
Painting.
The lips were painted in a purple basecoat, followed up with some inking in purple and black and drybrushing to lighter colours. The lips are ever so slightly a different shade against the other skin region, again to differentiate them from the upper lip / moustache region. The teeth were done in creams, yellows, and some browns to create the look of someone who could do with a swift visit to the dentist.
Evaluation.
A little bit of observation of the real world can contribute immensely to conversions like this. I really like this rhino and try to use it in games as often as possible as a result.