No, actually, a critter with elongated fingerbones could not glide. The mechanisms for gliding and winged flight are very different, that is my whole point. Gliding is not primitive flight, it is a separate means of locomotion. Heat sensitive "eye-spots" are not primitive eyes, they are a different mode of perception. Reptilian hearts are not primitive mammalian hearts, they are different form of circulatory pump. The snout of a tapir is not a primitive form of an elephant's trunk, different muscle groups and bone attachments are used. The evolutionary chain simply isn't there, and grouping animals that look somewhat alike doesn't qualify.