Thanks to @texasturtles !!
I was very fortunate to photograph 3 Alligators Snapping turtles and one Mississippi Map turtle yesterday.
This is the first one that they found, a smaller male Alligator Snapping turtle.
I was told this is a male. (see second picture)
While Carl was measuring the size of turtle, and I took some pictures with 100mm Marco lens. I don't think it's a good idea to get very close to a snapping turtle's face with a cell phone camera.
The back (dorsal) part of the shell was rough and angular, not rounded.