Some of these, to be sure, would be guesses, some could be determined by having a physical model of the skeleton on one's desk so that one could (like Ray Harryhausen or Willis O'Brien) actually manipulate the skeleton. One could see how far a head and jaws could open and move, judge the possible area and volume of lungs (= inferring strength of vocals), see the limits of movement ranges of wings (arms with feathers).