Yep, it is a really common thing for males to do. You will see male dogs do this regularly when breeding season approaches as they check the urine of females to see if they are receptive. A lot of dogs generalize the behavior to something they do when they are just plain excited.
Max would do this when he found what was probably female in heat urine on our walks. It was so funny! That was the only time he ever did it. I haven't seen Tyler do it at all. Max was neutered, and so is Tyler. Zoey smacks her lips when she's excited–usually when she's waiting for a treat.
My female does it when she is playing hard or fighting with with other dogs (male or female) and I saw her do it once after beating up the cat we have (also a male). I've been told that females do it as a sign of sexual arousal. But I just watched (5 minutes ago) her do it after fighting with our male pup. really looking for some clarification on this.
I have seen Mica when she goes on point with her tail straight out and her front and back paws CAREFULLY matching each step chatter her jaw - It kind of goes open and shut and wanders open and shut that way. She is like an arrow waiting to fly out of the bow onto the suspected target. She never stops that behavior, either. Than she makes a mad dash for the squirrel or critter and will do doggie-ups on the side of a tree - maybe 6-8 feet up the side than down. Than shell do it again just because she has to try again. I think she is getting some really strong chest muscles. I think it might me intense excitement and anticipation.