Let me clarify first of all that this issue is VERY INSIGNIFICANT compared some of the other issues that need to be fixed in this game. That being said: several species that should have dental pads (rather than upper front teeth) have tooth-like coloring in that spot.
They aren't shaped like teeth so I'm thinking the models are largely correct and there was just some confusion when it came to the textures. Most of the cervids seem correct other than the mule deer, but several of the bovids have the issue, including the Cape buffalo, ibexes, mouflon, wildebeest, and gemsbok. This isn't a comprehensive list, I was just poking around in the mouths of the trophies I have in my lodge, which isn't all the relevant species.
I'm hoping the trend of updating the visuals for the various species continues, and perhaps adjusting the mouth textures to accurately reflect dental pads could be part of that.