Yawning behavior has been widely observed among extant vertebrates and the behavior has been associated with a variety of different stimuli such as sleepiness, stress, or social displays. The large, exaggerated mouth gape characteristic of yawning distorts the soft tissues of the face in mammals, including the facial muscles. The facial muscles of the upper lip and snout are responsible for the movement and structural composition of the elongated, mobile nasal proboscis found independently in multiple lineages of mammals including sengi (Macroscelidea), elephants (Proboscidea), solenodon (Eulipotyphla, Solenodontidae), desmans (Eulipotyphla, Talpidae), tapirs (Perissodactyla), and saiga antelope (Artiodactyla). Despite the repeated evolution of a mobile nasal proboscis, there is considerable diversity in the muscular anatomy, internal support structures, and overall morphology of these appendages which may be reflected in behaviors such as yawning. Using categorical scoring of the movement and position of the proboscis during yawning in video recordings, I found little intraspecific variation, but notable differences between species, even among relatively closely related taxa: e.g., between members of the sengi subfamily Rhynchocyoninae yawning with a “snout down” position versus subfamily Macroscelidinae yawning with a “snout up” position. In this study, I present a characterization of the morphological diversity of mammalian nasal probosces, their potential impact upon yawning behavior, and the use of the online video sharing platform YouTube, a rich and relatively untapped source of publicly-accessible data on animal behavior and function.