The meadow that Lower Gaylor Lake inhabits is home to more than a meadow's normal share of boulders. I haven't found an explanation in the otherwise excellent Geology Underfoot in Yosemite National Park or on Garry Hayes's geology blog, so I'm going to speculate and say they're troll molars. Occam's razor in action!
Being as big a chicken as anyone when it comes to hiking home alone in the dark, I was too worried about the retreating daylight to bother setting up the tripod for this shot - you don't want to go mounting an expensive camera on something that, at any moment, you might need handy for fending off slavering bands of rabid vampire marmots - and the resulting harm to the picture's overall sharpness and noise levels necessitated a certain amount of Photoshop triage. Many CPU cycles died to bring you this photo.