Yak vs Muskox? Gamera Explains!
On the viewer's left: a yak.
On the viewer's right: a muskox.
There, now you know the difference.
(I do wish I could find a yak that looked more like this one though.)
Why is Gamera chiming in? He's actually helpful like that. Also he had nothing better to do.
(I just got a new phone so this is all an excuse to mess about with it. Randomly the yak and muskox are always kept together on my desk to compare and contrast.)