:the plastral shot would also show the number of hinges, and allow the determination between mud and musk.... their carapaces are pretty similar.
Actually I am going by the fact that we can see the plastron (with the end obviously has a strong hinge) and the length of the bridge from the angle of the photo suggests very strongly that it is a mud turtle, not a musk turtle. Musk turtles have plastrons similar to snapping turtles...which is hardly nothing there unless you flip them over to see it. I like to think of it as mud turtles wearing a normal tshirt while musk turtles wear those bodybuilder tank tops. In this instance, it would be helpful to be able to see the entire look of the plastron as the shape of the plates are usually different enough in the species/subspecies of mud turtles to be able figure out what it is.