I think both sexes of all U.S. mud/musk turtles have terminal spines on their tails. But the males are much larger.
However, an adult male yellow mud turtle will also have a tail that is just about like your pinky finger in shape and size. The terminal spine is the LEAST noticeable feature! Females have little nothing tails with a little spine at the tip. But males have huge tails...you can't miss it.